Science.gov

Sample records for elevated-temperature structural materials

  1. Elevated Temperature Crack Growth Behavior in HSCT Structural Materials

    NASA Technical Reports Server (NTRS)

    Saxena, Ashok

    1998-01-01

    Structures in super-sonic aircraft are subjected to conditions of high temperature and cyclic and sustained loading for extended periods of time. The durability of structures fabricated from aluminum and certain titanium alloys in such demanding conditions is of primary concern to the designers and manufacturers of futuristic transport aircraft. Accordingly, the major goal of this project was to evaluate the performance and durability of high temperature aluminum and titanium alloys for use in high speed civil transport (HSCT) structures. Additional goals were to develop time-dependent fracture mechanics methodology and test methods for characterizing and predicting elevated temperature crack growth behavior in creep-brittle materials such as ones being considered for use in HSCT structures and to explore accelerated methods of simulating microstructural degradation during service and measuring degraded properties in these materials.

  2. The Effect of Elevated Temperature on Concrete Materials and Structures - a Literature Review.

    SciTech Connect

    Naus, Dan J

    2006-03-01

    The objective of this limited study was to provide an overview of the effects of elevated temperature on the behavior of concrete materials and structures. In meeting this objective the effects of elevated temperatures on the properties of ordinary Portland cement concrete constituent materials and concretes are summarized. The effects of elevated temperature on high-strength concrete materials are noted and their performance compared to normal strength concretes. A review of concrete materials for elevated-temperature service is presented. Nuclear power plant and general civil engineering design codes are described. Design considerations and analytical techniques for evaluating the response of reinforced concrete structures to elevated-temperature conditions are presented. Pertinent studies in which reinforced concrete structural elements were subjected to elevated temperatures are described.

  3. "Ultra"-Fast Fracture Strength of Advanced Structural Ceramic Materials Studied at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Gyekenyesi, John P.

    1999-01-01

    The accurate determination of inert strength is important in reliable life prediction of structural ceramic components. At ambient temperature, the inert strength of a brittle material is typically regarded as free of the effects of slow crack growth due to stress corrosion. Therefore, the inert strength can be determined either by eliminating active species, especially moisture, with an appropriate inert medium, or by using a very high test rate. However, at elevated temperatures, the concept or definition of the inert strength of brittle ceramic materials is not clear, since temperature itself is a degrading environment, resulting in strength degradation through slow crack growth and/or creep. Since the mechanism to control strength is rate-dependent viscous flow, the only conceivable way to determine the inert strength at elevated temperatures is to utilize a very fast test rate that either minimizes the time for or eliminates slow crack growth. Few experimental studies have measured the elevated-temperature, inert (or "ultra"-fast fracture) strength of advanced ceramics. At the NASA Lewis Research Center, an experimental study was initiated to better understand the "ultra"-fast fracture strength behavior of advanced ceramics at elevated temperatures. Fourteen advanced ceramics - one alumina, eleven silicon nitrides, and two silicon carbides - have been tested using constant stress-rate (dynamic fatigue) testing in flexure with a series of stress rates including the "ultra"-fast stress rate of 33 000 MPa/sec with digitally controlled test frames. The results for these 14 advanced ceramics indicate that, notwithstanding possible changes in flaw populations as well as flaw configurations because of elevated temperatures, the strength at 33 000 MPa/sec approached the room-temperature strength or reached a higher value than that determined at the conventional test rate of 30 MPa/sec. On the basis of the experimental data, it can be stated that the elevated-temperature

  4. Elevated-Temperature Tribology of Metallic Materials

    SciTech Connect

    Blau, Peter Julian

    2010-01-01

    The wear of metals and alloys takes place in many forms, and the type of wear that dominates in each instance is influenced by the mechanics of contact, material properties, the interfacial temperature, and the surrounding environment. The control of elevated-temperature friction and wear is important for applications like internal combustion engines, aerospace propulsion systems, and metalworking equipment. The progression of interacting, often synergistic processes produces surface deformation, subsurface damage accumulation, the formation of tribolayers, and the creation of free particles. Reaction products, particularly oxides, play a primary role in debris formation and microstructural evolution. Chemical reactions are known to be influenced by the energetic state of the exposed surfaces, and that surface energy is in turn affected by localized deformation and fracture. At relatively low temperatures, work-hardening can occur beneath tribo-contacts, but exposure to high temperatures can modify the resultant defect density and grain structure to affect the mechanisms of re-oxidation. As research by others has shown, the rate of wear at elevated temperatures can either be enhanced or reduced, depending on contact conditions and nature of oxide layer formation. Furthermore, the thermodynamic driving force for certain chemical reactions is moderated by kinetics and microstructure. The role of deformation, oxidation, and tribo-corrosion in the elevated temperature tribology of metallic alloys will be exemplified by three examples involving sliding wear, single-point abrasion, and repetitive impact plus slip.

  5. Methods for structural design at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Ellison, A. M.; Jones, W. E., Jr.; Leimbach, K. R.

    1973-01-01

    A procedure which can be used to design elevated temperature structures is discussed. The desired goal is to have the same confidence in the structural integrity at elevated temperature as the factor of safety gives on mechanical loads at room temperature. Methods of design and analysis for creep, creep rupture, and creep buckling are presented. Example problems are included to illustrate the analytical methods. Creep data for some common structural materials are presented. Appendix B is description, user's manual, and listing for the creep analysis program. The program predicts time to a given creep or to creep rupture for a material subjected to a specified stress-temperature-time spectrum. Fatigue at elevated temperature is discussed. Methods of analysis for high stress-low cycle fatigue, fatigue below the creep range, and fatigue in the creep range are included. The interaction of thermal fatigue and mechanical loads is considered, and a detailed approach to fatigue analysis is given for structures operating below the creep range.

  6. Aircraft structures research at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Duberg, John E

    1955-01-01

    A review is made of the test techniques that have been developed and used by the NACA for experimental research in aircraft structures at elevated temperatures. Some experimental results are presented. Remarks are included on the problem of model scaling for testing of structures at high temperatures. (author)

  7. 49 CFR 172.325 - Elevated temperature materials.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 2 2014-10-01 2014-10-01 false Elevated temperature materials. 172.325 Section... REQUIREMENTS, AND SECURITY PLANS Marking § 172.325 Elevated temperature materials. (a) Except as provided in paragraph (b) of this section, a bulk packaging containing an elevated temperature material must be...

  8. 49 CFR 172.325 - Elevated temperature materials.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 2 2011-10-01 2011-10-01 false Elevated temperature materials. 172.325 Section... REQUIREMENTS, AND SECURITY PLANS Marking § 172.325 Elevated temperature materials. (a) Except as provided in paragraph (b) of this section, a bulk packaging containing an elevated temperature material must be...

  9. 49 CFR 172.325 - Elevated temperature materials.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 2 2013-10-01 2013-10-01 false Elevated temperature materials. 172.325 Section... REQUIREMENTS, AND SECURITY PLANS Marking § 172.325 Elevated temperature materials. (a) Except as provided in paragraph (b) of this section, a bulk packaging containing an elevated temperature material must be...

  10. 49 CFR 172.325 - Elevated temperature materials.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Elevated temperature materials. 172.325 Section... REQUIREMENTS, AND SECURITY PLANS Marking § 172.325 Elevated temperature materials. (a) Except as provided in paragraph (b) of this section, a bulk packaging containing an elevated temperature material must be...

  11. 49 CFR 172.325 - Elevated temperature materials.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Elevated temperature materials. 172.325 Section... REQUIREMENTS, AND SECURITY PLANS Marking § 172.325 Elevated temperature materials. (a) Except as provided in paragraph (b) of this section, a bulk packaging containing an elevated temperature material must be...

  12. The emittance of space radiator materials measured at elevated temperatures

    SciTech Connect

    Mirtich, M.J.; DiFilippo, F.; Barry, J.; Kussmaul, M.

    1994-09-01

    The spectral emittances of textured space radiator materials between 1.7 and 14.7 {mu}m have been evaluated at room temperature and elevated temperature (630{degrees}C) in air. Heating in air caused a permanent increase in spectral emittance for all materials tested: HCl/ion beam textured 304 stainless steel, untextured Ti (6 percent Al, 4 percent V), and sandblasted Ti (6 percent Al, 4 percent V). Changes in the surface chemistry and/or surface morphology of these materials were also observed. Elevated temperature spectral emittance was measured in an argon atmosphere and compared to the measurements in air. Similarity between the room temperature and elevated temperature spectral emittance measurements was also investigated, and limited agreement was found.

  13. Elevated Temperature Testing and Modeling of Advanced Toughened Ceramic Materials

    NASA Technical Reports Server (NTRS)

    Keith, Theo G.

    2005-01-01

    The purpose of this report is to provide a final report for the period of 12/1/03 through 11/30/04 for NASA Cooperative Agreement NCC3-776, entitled "Elevated Temperature Testing and Modeling of Advanced Toughened Ceramic Materials." During this final period, major efforts were focused on both the determination of mechanical properties of advanced ceramic materials and the development of mechanical test methodologies under several different programs of the NASA-Glenn. The important research activities made during this period are: 1. Mechanical properties evaluation of two gas-turbine grade silicon nitrides. 2) Mechanical testing for fuel-cell seal materials. 3) Mechanical properties evaluation of thermal barrier coatings and CFCCs and 4) Foreign object damage (FOD) testing.

  14. Structural efficiencies of various aluminum, titanium, and steel alloys at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Heimerl, George J; Hughes, Philip J

    1953-01-01

    Efficient temperature ranges are indicated for two high-strength aluminum alloys, two titanium alloys, and three steels for some short-time compression-loading applications at elevated temperatures. Only the effects of constant temperatures and short exposure to temperature are considered, and creep is assumed not to be a factor. The structural efficiency analysis is based upon preliminary results of short-time elevated-temperature compressive stress-strain tests of the materials. The analysis covers strength under uniaxial compression, elastic stiffness, column buckling, and the buckling of long plates in compression or in shear.

  15. The effects of elevated temperatures on the structural properties of fiber composite materials suitable for use in space shuttle and other space vehicles

    NASA Technical Reports Server (NTRS)

    Wright, M. A.

    1972-01-01

    The effects of high temperatures on the structural properties of fiber composite materials for use in spacecraft structures are investigated. Various mechanical properties of boron reinforced aluminum alloys were measured. It was observed that cycling these materials through temperatures that varied from room temperature to 425 C could seriously degrade the properties. The extent of the observed effects depended on alloy type and the maximum cyclic temperature used. Results are discussed in terms of upper and lower strength bonds calculated from the strengths of individual fibers.

  16. 49 CFR 173.247 - Bulk packaging for certain elevated temperature materials.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 101 and IM 102 portable tanks; UN portable tanks; marine portable tanks conforming to 46 CFR part 64... 49 Transportation 2 2013-10-01 2013-10-01 false Bulk packaging for certain elevated temperature... Than Class 1 and Class 7 § 173.247 Bulk packaging for certain elevated temperature materials....

  17. 49 CFR 173.247 - Bulk packaging for certain elevated temperature materials.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 101 and IM 102 portable tanks; UN portable tanks; marine portable tanks conforming to 46 CFR part 64... 49 Transportation 2 2011-10-01 2011-10-01 false Bulk packaging for certain elevated temperature... Than Class 1 and Class 7 § 173.247 Bulk packaging for certain elevated temperature materials....

  18. 49 CFR 173.247 - Bulk packaging for certain elevated temperature materials.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 101 and IM 102 portable tanks; UN portable tanks; marine portable tanks conforming to 46 CFR part 64... 49 Transportation 2 2012-10-01 2012-10-01 false Bulk packaging for certain elevated temperature... Than Class 1 and Class 7 § 173.247 Bulk packaging for certain elevated temperature materials....

  19. 49 CFR 173.247 - Bulk packaging for certain elevated temperature materials.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 101 and IM 102 portable tanks; UN portable tanks; marine portable tanks conforming to 46 CFR part 64... 49 Transportation 2 2014-10-01 2014-10-01 false Bulk packaging for certain elevated temperature... Than Class 1 and Class 7 § 173.247 Bulk packaging for certain elevated temperature materials....

  20. Design and analysis of aerospace structures at elevated temperatures. [aircraft, missiles, and space platforms

    NASA Technical Reports Server (NTRS)

    Chang, C. I.

    1989-01-01

    An account is given of approaches that have emerged as useful in the incorporation of thermal loading considerations into advanced composite materials-based aerospace structural design practices. Sources of structural heating encompass not only propulsion system heat and aerodynamic surface heating at supersonic speeds, but the growing possibility of intense thermal fluxes from directed-energy weapons. The composite materials in question range from intrinsically nonheat-resistant polymer matrix systems to metal-matrix composites, and increasingly to such ceramic-matrix composites as carbon/carbon, which are explicitly intended for elevated temperature operation.

  1. Shell structures in aluminum nanocontacts at elevated temperatures.

    PubMed

    Costa-Krämer, José Luis; León, Natalia; Guerrero, Carlo; Díaz, Marisel

    2012-01-01

    Aluminum nanocontact conductance histograms are studied experimentally from room temperature up to near the bulk melting point. The dominant stable configurations for this metal show a very early crossover from shell structures at low wire diameters to ionic subshell structures at larger diameters. At these larger radii, the favorable structures are temperature-independent and consistent with those expected for ionic subshell (faceted) formations in face-centered cubic geometries. When approaching the bulk melting temperature, these local stability structures become less pronounced as shown by the vanishing conductance histogram peak structure. PMID:22325572

  2. 49 CFR 173.247 - Bulk packaging for certain elevated temperature materials.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 101 and IM 102 portable tanks; UN portable tanks; marine portable tanks conforming to 46 CFR part 64... 49 Transportation 2 2010-10-01 2010-10-01 false Bulk packaging for certain elevated temperature... SHIPPERS-GENERAL REQUIREMENTS FOR SHIPMENTS AND PACKAGINGS Bulk Packaging for Hazardous Materials...

  3. Diamond structure recovery during ion irradiation at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Deslandes, Alec; Guenette, Mathew C.; Belay, Kidane; Elliman, Robert G.; Karatchevtseva, Inna; Thomsen, Lars; Riley, Daniel P.; Lumpkin, Gregory R.

    2015-12-01

    CVD diamond is irradiated by 5 MeV carbon ions, with each sample held at a different temperature (300-873 K) during irradiations. The defect structures resulting from the irradiations are evident as vacancy, interstitial and amorphous carbon signals in Raman spectra. The observed variation of the full width at half maximum (FWHM) and peak position of the diamond peak suggests that disorder in the diamond lattice is reduced for high temperature irradiations. The dumbbell interstitial signal is reduced for irradiations at 873 K, which suggests this defect is unstable at these temperatures and that interstitials have migrated to crystal surfaces. Near edge X-ray absorption fine structure (NEXAFS) spectroscopy results indicate that damage to the diamond structure at the surface has occurred for room temperature irradiations, however, this structure is at least partially recovered for irradiations performed at 473 K and above. The results suggest that, in a high temperature irradiation environment such as a nuclear fusion device, in situ annealing of radiation-created defects can maintain the diamond structure and prolong the lifetime of diamond components.

  4. Geopolymeric materials prepared using Class F fly ash and elevated temperature curing

    SciTech Connect

    Bakharev, T. . E-mail: tanya.bakharev@eng.monash.edu.au

    2005-06-01

    This paper reports the results of the study of the influence of elevated temperature curing on phase composition, microstructure and strength development in geopolymer materials prepared using Class F fly ash and sodium silicate and sodium hydroxide solutions. In particular, the effect of storage at room temperature before the application of heat on strength development and phase composition was studied. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and SEM were utilised in this study. Long precuring at room temperature before application of heat was beneficial for strength development in all studied materials, as strength comparable to 1 month of curing at elevated temperature can develop in this case only after 24 h of heat curing. The main product of reaction in the geopolymeric materials was amorphous alkali aluminosilicate gel. However, in the case of sodium hydroxide activator in addition to it, traces of chabazite, Linde Type A, Na-P1 (gismondine) zeolites and hydroxysodalite were also present. The type of zeolite present and composition of aluminosilicate gel were dependent on the curing history.

  5. Material property data and their use in design and analysis for an elevated temperature solar code

    NASA Astrophysics Data System (ADS)

    Berman, I.

    1981-11-01

    Specific properties of the materials, temperatures, and operating parameters for elevated temperature solar thermal power plants are considered as a basis for developing standards of implementation. Physical and mechanical properties such as thermal conductivity, elastic modulus, expansion, strength, and creep are discussed and recommendations for ASME Code I and III materials are cited where feasible. Inelastic behavior tests involving beam bending, pipe ratcheting, torsion-torsion tests, and axial cyclic tests of various stainless steel specimens and Incoloy 800 material are reported. Peculiarities of problems for solar applications are noted to be a lack of information of basic material behavior due to the low amount of actual operational experience, a large number of transient temperature cycles, and primary creep.

  6. Composition of sputtered material from CuNi alloy during Xe + ion sputtering at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Sekine, Shigeyuki; Shimizu, Hazime; Ichimura, Singo

    1995-04-01

    Polycrystalline CuNi alloys were sputtered by 3 kV Xe + ions at elevated temperatures to analyze the ion-beam-induced diffusion. The time evolution of the composition of the sputtered materials from the start of the sputtering was measured by TOF-SNMS (time-of-flight sputtered neutral mass spectrometry). During removal of the Gibbsian segregation layer of copper, the sputtered flux consisted of almost only copper atoms. Then, the copper content gradually decreased due to the formation of a sputter-induced copper-depleted surface layer, and reached an almost steady state with still higher copper content than the bulk composition. From the temperature dependence of the composition at the quasi-steady state the activation energy of copper transportation through a high diffusivity path was derived to be 54 kJ mol -1 (0.56 eV). The high diffusivity path was assigned to copper diffusion through grain boundaries.

  7. Reliability and life prediction of ceramic composite structures at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Duffy, Stephen F.; Gyekenyesi, John P.

    1994-01-01

    Methods are highlighted that ascertain the structural reliability of components fabricated of composites with ceramic matrices reinforced with ceramic fibers or whiskers and subject to quasi-static load conditions at elevated temperatures. Each method focuses on a particular composite microstructure: whisker-toughened ceramics, laminated ceramic matrix composites, and fabric reinforced ceramic matrix composites. In addition, since elevated service temperatures usually involve time-dependent effects, a section dealing with reliability degradation as a function of load history has been included. A recurring theme throughout this chapter is that even though component failure is controlled by a sequence of many microfailure events, failure of ceramic composites will be modeled using macrovariables.

  8. Effect of Preloading on Fatigue Strength in Dynamic Fatigue Testing of Ceramic Materials at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Salem, Jonathan A.

    1995-01-01

    Previously derived solutions of fatigue strength as a function of preloading were verified by applying preloads to elevated temperature dynamic fatigue tests of 96 wt% alumina at 1000 C and NC 132 silicon nitride at 1100 C. The technique was found very useful in identification and control of the governing failure mechanism when multiple failure mechanisms, such as slow crack growth, creep and oxidation occurred simultaneously at elevated temperatures.

  9. Evaluation of pore structures and cracking in cement paste exposed to elevated temperatures by X-ray computed tomography

    SciTech Connect

    Kim, Kwang Yeom; Yun, Tae Sup; Park, Kwang Pil

    2013-08-15

    When cement-based materials are exposed to the high temperatures induced by fire, which can rapidly cause temperatures of over 1000 °C, the changes in pore structure and density prevail. In the present study, mortar specimens were subjected to a series of increasing temperatures to explore the temperature-dependent evolution of internal pore structure. High-performance X-ray computed tomography (CT) was used to observe the evolution of temperature-induced discontinuities at the sub-millimeter level. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to investigate the cause of physical changes in the heated mortar specimens. Results exhibit the changes in pore structure caused by elevated temperatures, and thermally induced fractures. We discuss the progressive formation of thermally induced fracture networks, which is a prerequisite for spalling failure of cement-based materials by fire, based on visual observations of the 3D internal structures revealed by X-ray CT.

  10. Apparatus for Measuring Spectral Emissivity of Solid Materials at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Ren, Dengfeng; Tan, Hong; Xuan, Yimin; Han, Yuge; Li, Qiang

    2016-05-01

    Spectral emissivity measurements at high temperature are of great importance for both scientific research and industrial applications. A method to perform spectral emissivity measurements is presented based on two sample heating methods, the flat plate and tubular furnace. An apparatus is developed to measure the normal spectral emissivity of solid material at elevated temperatures from 1073 K to 1873 K and wavelengths from 2 \\upmu hbox {m} to 25 \\upmu hbox {m}. Sample heating is accomplished by a torch flame or a high temperature furnace. Two different variable temperature blackbody sources are used as standard references and the radiance is measured by a FTIR spectrometer. Following calibration of the spectral response and background radiance of the spectrometer, the effect of the blackbody temperature interval on calibration results is discussed. Measurements are performed of the normal spectral emissivity of SiC and graphite over the prescribed temperature and wavelength range. The emissivity of SiC at high temperatures is compared with the emissivity at room temperature, and the influence of an oxide layer formed at the surface of SiC on the emissivity is studied. The effect of temperature on the emissivity of graphite is also investigated. Furthermore, a thorough analysis of the uncertainty components of the emissivity measurement is performed.

  11. Structural characteristics and elevated temperature mechanical properties of AJ62 Mg alloy

    SciTech Connect

    Kubásek, J. Vojtěch, D.; Martínek, M.

    2013-12-15

    Structure and mechanical properties of the novel casting AJ62 (Mg–6Al–2Sr) alloy developed for elevated temperature applications were studied. The AJ62 alloy was compared to commercial casting AZ91 (Mg–9Al–1Zn) and WE43 (Mg–4Y–3RE) alloys. The structure was examined by scanning electron microscopy, x-ray diffraction and energy dispersive spectrometry. Mechanical properties were characterized by Viskers hardness measurements in the as-cast state and after a long-term heat treatment at 250 °C/150 hours. Compressive mechanical tests were also carried out both at room and elevated temperatures. Compressive creep tests were conducted at a temperature of 250 °C and compressive stresses of 60, 100 and 140 MPa. The structure of the AJ62 alloy consisted of primary α-Mg dendrites and interdendritic nework of the Al{sub 4}Sr and massive Al{sub 3}Mg{sub 13}Sr phases. By increasing the cooling rate during solidification from 10 and 120 K/s the average dendrite arm thickness decreased from 18 to 5 μm and the total volume fraction of the interdendritic phases from 20% to 30%. Both factors slightly increased hardness and compressive strength. The room temperature compressive strength and hardness of the alloy solidified at 30 K/s were 298 MPa and 50 HV 5, i.e. similar to those of the as-cast WE43 alloy and lower than those of the AZ91 alloy. At 250 °C the compressive strength of the AJ62 alloy decreased by 50 MPa, whereas those of the AZ91 and WE43 alloys by 100 and 20 MPa, respectively. The creep rate of the AJ62 alloy was higher than that of the WE43 alloy, but significantly lower in comparison with the AZ91 alloy. Different thermal stabilities of the alloys were discussed and related to structural changes during elevated temperature expositions. - Highlights: • Small effect of cooling rate on the compressive strength and hardness of AJ 62 • A bit lower compressive strength of AJ 62 compared to AZ91 at room temperature • Higher resistance of the AJ 62

  12. Microwave-enhanced electrochemical cycling performance of the LiNi0.2Mn1.8O4 spinel cathode material at elevated temperature.

    PubMed

    Raju, Kumar; Nkosi, Funeka P; Viswanathan, Elumalai; Mathe, Mkhulu K; Damodaran, Krishnan; Ozoemena, Kenneth I

    2016-05-14

    The well-established poor electrochemical cycling performance of the LiMn2O4 (LMO) spinel cathode material for lithium-ion batteries at elevated temperature stems from the instability of the Mn(3+) concentration. In this work, a microwave-assisted solid-state reaction has been used to dope LMO with a very low amount of nickel (i.e., LiNi0.2Mn1.8O4, herein abbreviated as LMNO) for lithium-ion batteries from Mn3O4 which is prepared from electrolytic manganese oxide (EMD, γ-MnO2). To establish the impact of microwave irradiation on the electrochemical cycling performance at an elevated temperature (60 °C), the Mn(3+) concentration in the pristine and microwave-treated LMNO samples was independently confirmed by XRD, XPS, (6)LiMAS-NMR and electrochemical studies including electrochemical impedance spectroscopy (EIS). The microwave-treated sample (LMNOmic) allowed for the clear exposure of the {111} facets of the spinel, optimized the Mn(3+) content, promoting structural and cycle stability at elevated temperature. At room temperature, both the pristine (LMNO) and microwave-treated (LMNOmic) samples gave comparable cycling performance (>96% capacity retention and ca. 100% coulombic efficiency after 100 consecutive cycling). However, at an elevated temperature (60 °C), the LMNOmic gave an improved cycling stability (>80% capacity retention and ca. 90% coulombic efficiency after 100 consecutive cycling) compared to the LMNO. For the first time, the impact of microwave irradiation on tuning the average manganese redox state of the spinel material to enhance the cycling performance of the LiNi0.2Mn1.8O4 at elevated temperature and lithium-ion diffusion kinetics has been clearly demonstrated. PMID:27113855

  13. Sandwich-structured polymer nanocomposites with high energy density and great charge-discharge efficiency at elevated temperatures.

    PubMed

    Li, Qi; Liu, Feihua; Yang, Tiannan; Gadinski, Matthew R; Zhang, Guangzu; Chen, Long-Qing; Wang, Qing

    2016-09-01

    The demand for a new generation of high-temperature dielectric materials toward capacitive energy storage has been driven by the rise of high-power applications such as electric vehicles, aircraft, and pulsed power systems where the power electronics are exposed to elevated temperatures. Polymer dielectrics are characterized by being lightweight, and their scalability, mechanical flexibility, high dielectric strength, and great reliability, but they are limited to relatively low operating temperatures. The existing polymer nanocomposite-based dielectrics with a limited energy density at high temperatures also present a major barrier to achieving significant reductions in size and weight of energy devices. Here we report the sandwich structures as an efficient route to high-temperature dielectric polymer nanocomposites that simultaneously possess high dielectric constant and low dielectric loss. In contrast to the conventional single-layer configuration, the rationally designed sandwich-structured polymer nanocomposites are capable of integrating the complementary properties of spatially organized multicomponents in a synergistic fashion to raise dielectric constant, and subsequently greatly improve discharged energy densities while retaining low loss and high charge-discharge efficiency at elevated temperatures. At 150 °C and 200 MV m(-1), an operating condition toward electric vehicle applications, the sandwich-structured polymer nanocomposites outperform the state-of-the-art polymer-based dielectrics in terms of energy density, power density, charge-discharge efficiency, and cyclability. The excellent dielectric and capacitive properties of the polymer nanocomposites may pave a way for widespread applications in modern electronics and power modules where harsh operating conditions are present. PMID:27551101

  14. Evaluation of a strain-gage load calibration on a low-aspect-ratio wing structure at elevated temperature

    NASA Technical Reports Server (NTRS)

    Reardon, Lawrence F.

    1989-01-01

    The environmental aspect of elevated temperature and its relationship to the science of strain gage calibrations of aircraft structures are addressed. A section of a wing designed for a high-speed aircraft structure was used to study this problem. This structure was instrumented with strain gages calibrated at both elevated and room temperatures. Load equations derived from a high-temperature load calibration were compared with equations derived from an identical load calibration at room temperature. The implications of the high temperature load calibration were studied from the viewpoint of applicability and necessity. Load equations derived from the room temperature load calibration resulted in generally lower equation standard errors than equations derived from the elevated temperature load calibration. A distributed load was applied to the structure at elevated temperature and strain gage outputs were measured. This applied load was then calculated using equations derived from both the room temperature and elevated temperature calibration data. It was found that no significant differences between the two equation systems existed in terms of computing this applied distributed load, as long as the thermal shifts resulting from thermal stresses could be identified. This identification requires a heating of the structure. Therefore, it is concluded that for this structure, a high temperature load calibration is not required. However, a heating of the structure is required to determine thermal shifts.

  15. Micro-structural optimization of polybenzimidazole-based membranes for H2/CO2 separation at elevated temperatures

    SciTech Connect

    Singh, Rajinder P; Li, Xin; Dudeck, Kevin W; Benicewicz, Brian C; Berchtold, Kathryn A

    2012-06-12

    There is compelling need to develop novel separation methods to improve the energy efficiency of synthesis (syn) gas processing operations including H{sub 2} and H{sub 2}/CO production to meet power, chemicals, and fuel producer needs, as well as carbon capture and removal of other undesirable syngas impurities. To be technically and economically viable, a successful separation method must be applicable to industrially relevant gas streams at realistic process conditions and compatible with large gas volumes. H{sub 2} selective membrane technology is a promising method for syngas separations at elevated temperatures (>150 C) that could be positioned upstream or downstream of one or more of the water-gas-shift reactors (WGSRs) or integrated with a WGSR depending on application specific syngas processing. Polybenzimidazole (PBI)-based polymer chemistries are exceptional candidates for H{sub 2}/CO{sub 2} separations at elevated temperatures. In general, these materials possess excellent chemical resistance, very high glass transition temperatures (> 400 C), good mechanical properties, and an appropriate level of processability. Although commercially available PBI polymers have demonstrated commercially attractive H{sub 2}/CO{sub 2} selectivity, their H{sub 2} permeability is low. Our team s employing structural and chemical manipulations to tailor the polymer free-volume achitecture with the ultimate goal of enhancing H{sub 2} permselectivity while retaining the inherent hermochemical stability characteristics of PBI. We will discuss our synthetic approaches and their influences on the gas transport behavior of these PBI-based materials. In general, a decrease in H{sub 2}/CO{sub 2} selectivity was observed with an increase in H{sub 2} permeability. H{sub 2} permeability and H{sub 2}/CO{sub 2} selectivity at 250 C ranged from 50 to 1000 barrer and 5 to 45, respectively.

  16. Effects of elevated temperatures on different restorative materials: An aid to forensic identification processes

    PubMed Central

    Pol, Chetan A.; Ghige, Suvarna K.; Gosavi, Suchitra R.; Hazarey, Vinay K.

    2015-01-01

    Background: Heat-induced alterations to dental and restorative materials can be of great interest to forensic dentistry. Knowing the specific optical behavior of dental materials can be of high importance as recognition of changes induced by high temperatures can lead to the determination of material which was used in a dental restoration, facilitating identification of burned human remains. Aim: To observe the effects of predetermined temperatures (200°C–400°C–600°C–800°C–1000°C) on unrestored teeth and different restorative materials macroscopically and then examine them under a stereomicroscope for the purpose of identification. Materials and Methods: The study was conducted on 375 extracted teeth which were divided into five groups of 75 teeth each as follows: group 1- unrestored teeth, group 2- teeth restored with all-ceramic crowns, Group 3- with class I silver amalgam filling, group 4- with class I composite restoration, and group 5- with class I glass ionomer cement restoration. Results: Unrestored and restored teeth display a series of specific macroscopic & stereomicroscopic structural changes for each range of temperature. Conclusion: Dental tissues and restorative materials undergo a series of changes which correlate well with the various temperatures to which they were exposed. These changes are a consequence of the nature of the materials and their physicochemical characteristics. PMID:26005305

  17. Elevated temperature crack growth

    NASA Technical Reports Server (NTRS)

    Yau, J. F.; Malik, S. N.; Kim, K. S.; Vanstone, R. H.; Laflen, J. H.

    1985-01-01

    The objective of the Elevated Temperature Crack Growth Project is to evaluate proposed nonlinear fracture mechanics methods for application to combustor liners of aircraft gas turbine engines. During the first year of this program, proposed path-independent (P-I) integrals were reviewed for such applications. Several P-I integrals were implemented into a finite-element postprocessor which was developed and verified as part of the work. Alloy 718 was selected as the analog material for use in the forthcoming experimental work. A buttonhead, single-edge notch specimen was designed and verified for use in elevated-temperature strain control testing with significant inelastic strains. A crack mouth opening displacement measurement device was developed for further use.

  18. CO{sub 2}-gasification reactivity of different carbonaceous materials at elevated temperatures

    SciTech Connect

    Gu, J.; Wu, S.; Wu, Y.; Gao, J.

    2009-07-01

    At the atmospheric pressure and at the temperatures between 1,223 and 1,673 K, the CO{sub 2} gasification reactivity of seven different carbonaceous materials comprising coal tar pitch coke, petroleum coke, natural graphite, carbon black and three coal chars was investigated by using thermogravimetric analysis. Their crystalline structures were analyzed by X-ray diffraction (XRD). It is found that the reactivity of the chars, pitch coke and petroleum coke produced from liquid phase carbonization, is several times poorer than that of the coal chars produced from solid phase carbonization and even lower than that of natural graphite. At the same time, it is obtained that under the condition of the chemical reaction control, the apparent activation energies of the former are in the range of 135.82-174.92 kJ/mol, while those of the latter are between 89.95 kJ/mol and 110.05 kJ/mol. Besides, the reactivity of the sample has a certain correlation with the crystalline structure of the sample, i.e., the larger the fraction of the relatively better crystalline structure is, the poorer the reactivity of the sample is.

  19. Chemical structure of cement aged at normal and elevated temperatures and pressures, Part II: Low permeability class G oilwell cement

    SciTech Connect

    Le Saout, Gwenn . E-mail: gwenn.lesaout@epfl.ch; Lecolier, Eric; Rivereau, Alain; Zanni, Helene

    2006-03-15

    Recently, Low Permeability Cement formulation has been developed for oilwell cementing. Therefore, it is important to understand the physical and chemical processes causing cement degradation in the downhole environment. In this study, we have characterised a Low Permeability Class G oilwell Cement immersed for one year in brine at T = 293 K, p = 10{sup 5} Pa and T = 353 K, p = 7 x 10{sup 6} Pa using {sup 29}Si, {sup 27}Al NMR and XRD techniques. Elevated temperature and pressure conditions increase the rate of the pozzolanic reaction and have significant effects on the polymerisation of C-S-H and on the incorporation of Al in the C-S-H structure. Leaching resulted in the formation of calcite and a more polymerised C-S-H with the appearance of tobermorite in the sample cured at elevated temperature and pressure.

  20. The viscoplastic behavior of SCS6/Ti-15-3 metal matrix composite materials at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Tuttle, Mark E.

    1988-01-01

    Titanium-based metal matrix composite materials (MMC'S) are being considered for use in the National Aerospace Plane. It is expected that these materials will be subjected to temperatures ranging up to about 820 C (1500 F). The present study was a preliminary investigation intended to quantify the level of viscoplastic behavior exhibited by SCS6/Ti-15-3 MMC's at elevated temperatures. The study consisted of a series of uniaxial creep/creep recovery tests. These tests were conducted in air at a temperature of 535 C (1000 F). Three distinct types of specimens were tested: Ti-15-3 heat matrix specimens (O2/plus or minus 45) sub s composite specimens, and (90 sub 2/plus or minus 45) sub s composite specimens. Tensile loads were applied to the specimens using a lever-arm creep frame equipped with a high temperature furnace. Specimen creep stains were monitored using an LVDT-based extensometer.

  1. Impact Testing of Stainless Steel Material at Room and Elevated Temperatures

    SciTech Connect

    Dana K. Morton; Spencer D. Snow; Tom E. Rahl; Robert K. Blandford

    2007-07-01

    Stainless steels are used for the construction of numerous spent nuclear fuel or radioactive material containers that may be subjected to high strains and moderate strain rates during accidental drop events. Mechanical characteristics of these base materials and their welds under dynamic loads in the strain rate range of concern are not well documented. However, three previous papers [1, 2, 3] reported on impact testing and analysis results performed at the Idaho National Laboratory using 304/304L and 316/316L stainless steel base material specimens that began the investigation of these characteristics. The goal of the work presented herein is to add the results of additional tensile impact testing for 304/304L and 316/316L stainless steel material specimens. Utilizing a drop-weight impact test machine and 1/4-inch to 1/2-inch thick dog-bone shaped test specimens, additional tests achieved target strain rates of 5, 10, and 22 per second at room temperature, 300, and 600 degrees Fahrenheit. Elevated true stress-strain curves for these materials at each designated strain rate and temperature are presented herein.

  2. Progress in understanding the mechanical behavior of pressure-vessel materials at elevated temperatures

    SciTech Connect

    Swindeman, R.W.; Brinkman, C.R.

    1981-01-01

    Progress during the 1970's on the production of high-temperature mechanical properties data for pressure vessel materials was reviewed. The direction of the research was toward satisfying new data requirements to implement advances in high-temperature inelastic design methods. To meet these needs, servo-controlled testing machines and high-resolution extensometry were developed to gain more information on the essential behavioral features of high-temperature alloys. The similarities and differences in the mechanical response of various pressure vessel materials were identified. High-temperature pressure vessel materials that have received the most attention included Type 304 stainless steel, Type 316 stainless steel, 2 1/4 Cr-1 Mo steel, alloy 800H, and Hastelloy X.

  3. Materials compatibility with oxidizer-rich gases at elevated temperatures and pressure

    NASA Technical Reports Server (NTRS)

    1989-01-01

    An investigation of oxygen compatibility and resistance to ignition of candidate materials for use in a liquid rocket engine designed to incorporate an oxidizer rich preburner-LOX turbopump configuration was discussed. The program was divided into two basic tasks. The first task was to develop a preliminary design of an oxidizer turbopump preburner section complete with thermal and MS Parameter analyses and to develop a conceptual design of the main injector with a preliminary engine specification as the final product. The second task was directed totally at testing materials in oxygen-rich environments.

  4. Elevated temperature erosion studies on some materials for high temperature applications

    SciTech Connect

    Zhou Jianren.

    1991-01-01

    The surface degradation of materials due to high temperature erosion or combined erosion corrosion is a serious problem in many industrial and aeronautical applications. As such, it has become an important design consideration in many situations. The materials investigated in the present studies are stainless steels, Ti-6Al-4V, alumina ceramics, with and without silicate glassy phase, and zirconia. These are some of the potential materials for use in the high temperature erosive-corrosive environments. The erosion or erosion-corrosion experiments were performed in a high temperature sand-blast type of test rig. The variables studied included the temperature, material composition, heat treatment condition, impingement velocity and angle, erodent concentration, etc. The morphological features of the eroded or eroded-corroded surfaces, substrate deformation, and oxide characteristics were studied by optical and scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, thermogravimetric analysis. The scratch test, single ball impact, and indentation tests were used to understand the behavior of oxide film in particle impacts. Based on these studies, the understanding of the mechanisms involved in the mechanical or combined mechanical and chemical actions in erosion was developed.

  5. Thermal Output of WK-Type Strain Gauges on Various Materials at Cryogenic and Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Kowalkowski, Matthew K.; Rivers, H. Kevin; Smith, Russell W.

    1998-01-01

    Strain gage apparent strain (thermal output) is one of the largest sources of error associated with the measurement of strain when temperatures and mechanical loads are varied. In this paper, experimentally determined apparent strains of WK-type strain gages, installed on both metallic and composite-laminate materials of various lay-ups and resin systems for temperatures ranging from -450 F to 230 F are presented. For the composite materials apparent strain in both the 0 ply orientation angle and the 90 ply orientation angle were measured. Metal specimens tested included: aluminum-lithium alloy (Al-LI 2195-T87), aluminum alloy (Al 2219-T87), and titanium alloy. Composite materials tested include: graphite-toughened-epoxy (IM7/997- 2), graphite-bismaleimide (IM7/5260), and graphite-K3 (IM7/K3B). The experimentally determined apparent strain data are curve fit with a fourth-order polynomial for each of the materials studied. The apparent strain data and the polynomials that are fit to the data are compared with those produced by the strain gage manufacturer, and the results and comparisons are presented. Unacceptably high errors between the manufacture's data and the experimentally determined data were observed (especially at temperatures below - 270-F).

  6. Simultaneous moduli measurement of elastic materials at elevated temperatures using an ultrasonic waveguide method.

    PubMed

    Periyannan, Suresh; Balasubramaniam, Krishnan

    2015-11-01

    A novel technique for simultaneously measuring the moduli of elastic isotropic material, as a function of temperature, using two ultrasonic guided wave modes that are co-generated using a single probe is presented here. This technique can be used for simultaneously measuring Young's modulus (E) and shear modulus (G) of different materials over a wide range of temperatures (35 °C-1200 °C). The specimens used in the experiments have special embodiments (for instance, a bend) at one end of the waveguide and an ultrasonic guided wave generator/detector (transducer) at the other end for obtaining reflected signals in a pulse-echo mode. The orientation of the transducer can be used for simultaneously generating/receiving the L(0,1) and/or T(0,1) using a single transducer in a waveguide on one end. The far end of the waveguides with the embodiment is kept inside a heating device such as a temperature-controlled furnace. The time of flight difference, as a function of uniform temperature distribution region (horizontal portion) of bend waveguides was measured and used to determine the material properties. Several materials were tested and the comparison between values reported in the literature and measured values were found to be in agreement, for both elastic moduli (E and G) measurements, as a function of temperature. This technique provides significant reduction in time and effort over conventional means of measurement of temperature dependence of elastic moduli. PMID:26628161

  7. Structure and elevated temperature properties of carbon-free ferritic alloys strengthened by a Laves phase

    NASA Technical Reports Server (NTRS)

    Bhandarkar, M. D.; Zackay, V. F.; Parker, E. R.; Bhat, M. S.

    1975-01-01

    A Laves phase, Fe2Ta, was utilized to obtain good elevated temperature properties in a carbon-free iron alloy containing 1 at. pct Ta and 7 at. pct Cr. Room temperature embrittlement resulting from the precipitation of the Laves phase at grain boundaries was overcome by spheroidizing the precipitate. This was accomplished by thermally cycling the alloys through the alpha to gamma transformation. The short-time yield strength of the alloys decreased very slowly with increase in test temperature up to 600 C, but above this temperature, the strength decreased rapidly. Results of constant load creep and stress rupture tests conducted at several temperatures and stresses indicated that the rupture and creep strengths of spheroidized 1 Ta-7 Cr alloy were higher than those of several commercial steels containing chromium and/or molybdenum carbides but lower than those of steels containing substantial amounts of tungsten and vanadium. When molybdenum was added to the base Fe-Ta-Cr alloy, the rupture and creep strengths were considerably increased.

  8. Elevated Temperature, Residual Compressive Strength of Impact-Damaged Sandwich Structure Manufactured Out-of-Autoclave

    NASA Technical Reports Server (NTRS)

    Grimsley, Brian W.; Sutter, James K.; Burke, Eric R.; Dixon, Genevieve D.; Gyekenyesi, Thomas G.; Smeltzer, Stanley S.

    2012-01-01

    Several 1/16th-scale curved sandwich composite panel sections of a 10 m diameter barrel were fabricated to demonstrate the manufacturability of large-scale curved sections using minimum gauge, [+60/-60/0]s, toughened epoxy composite facesheets co-cured with low density (50 kilograms per cubic meters) aluminum honeycomb core. One of these panels was fabricated out of autoclave (OoA) by the vacuum bag oven (VBO) process using Cycom(Registered Trademark) T40-800b/5320-1 prepreg system while another panel with the same lay-up and dimensions was fabricated using the autoclave-cure, toughened epoxy prepreg system Cycom(Registered Trademark) IM7/977-3. The resulting 2.44 m x 2 m curved panels were investigated by non-destructive evaluation (NDE) at NASA Langley Research Center (NASA LaRC) to determine initial fabrication quality and then cut into smaller coupons for elevated temperature wet (ETW) mechanical property characterization. Mechanical property characterization of the sandwich coupons was conducted including edge-wise compression (EWC), and compression-after-impact (CAI) at conditions ranging from 25 C/dry to 150 C/wet. The details and results of this characterization effort are presented in this paper.

  9. Tensile behavior of glass/ceramic composite materials at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Mandell, J. F.; Grande, D. H.; Jacobs, J.

    1987-01-01

    This paper describes the tensile behavior of high-temperature composite materials containing continuous Nicalon ceramic fiber reinforcement and glass and glass/ceramic matrices. The longitudinal properties of these materials can approach theoretical expectations for brittle matrix composites, failing at a strength and ultimate strain level consistent with those of the fibers. The brittle, high-modulus matrices result in a nonlinear stress-strain curve due to the onset of stable matrix cracking at 10 to 30 percent of the fiber strain to failure, and at strains below this range in off-axis plies. Current fibers and matrices can provide attractive properties well above 1000 C, but composites experience embrittlement in oxidizing atmospheres at 800 to 1000 C due to oxidation of a carbon interface reaction layer.The oxidation effect greatly increases the interface bond strength, causing composite embrittlement.

  10. Electrical Properties of Materials for Elevated Temperature Resistance Strain Gage Application. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Lei, Jih-Fen

    1987-01-01

    The objective was to study the electrical resistances of materials that are potentially useful as resistance strain gages at 1000 C. Transition metal carbides and nitrides, boron carbide and silicon carbide were selected for the experimental phase of this research. Due to their low temperature coefficient of resistance and good stability, TiC, ZrC, B sub 4 C and beta-SiC are suggested as good candidates for high temperature resistance strain gage applications.

  11. Design Issues for Using Magnetic Materials in Radiation Environments at Elevated Temperature

    NASA Technical Reports Server (NTRS)

    Bowman, Cheryl L.

    2013-01-01

    One of the challenges of designing motors and alternators for use in nuclear powered space missions is accounting for the effects of radiation. Terrestrial reactor power plants use distance and shielding to minimize radiation damage but space missions must economize volume and mass. Past studies have shown that sufficiently high radiation levels can affect the magnetic response of hard and soft magnetic materials. Theoretical models explaining the radiation-induced degradation have been proposed but not verified. This paper reviews the literature and explains the cumulative effects of temperature, magnetic-load, and radiation-level on the magnetic properties of component materials. Magnetic property degradation is very specific to alloy choice and processing history, since magnetic properties are very much entwined with specific chemistry and microstructural features. However, there is basic theoretical as well as supportive experimental evidence that the negative impact to magnetic properties will be minimal if the bulk temperature of the material is less than fifty percent of the Curie temperature, the radiation flux is low, and the demagnetization field is small. Keywords: Magnets, Permanent Magnets, Power Converters, Nuclear Electric Power Generation, Radiation Tolerance.

  12. Consideration of Conductive Motor Winding Materials at Room and Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    de Groh, Henry C., III

    2015-01-01

    A brief history of conductive motor winding materials is presented, comparing various metal motor winding materials and their properties in terms of conductivity, density and cost. The proposed use of carbon nanotubes (CNTs) and composites incorporating CNTs is explored as a potential way to improve motor winding conductivity, density, and reduce motor size which are important to electric aircraft technology. The conductivity of pure Cu, a CNT yarn, and a dilute Cu-CNT composite was measured at room temperature and at several temperatures up to 340 C. The conductivity of the Cu-CNT composite was about 3 percent lower than pure copper's at all temperatures measured. The conductivity of the CNT yarn was about 200 times lower than copper's, however, the yarn's conductivity dropped less with increasing temperature compared to Cu. It is believed that the low conductivity of the yarn is due primarily to high interfacial resistances and the presence of CNTs with low, semiconductor like electrical properties (s-CNT). It is believed the conductivity of the CNT-Cu composite could be improved by not using s-CNT, and instead using only CNTs with high, metallic like electrical properties (m-CNT); and by increasing the vol% m-CNTs.

  13. Alterations in gill structure in tropical reef fishes as a result of elevated temperatures.

    PubMed

    Bowden, A J; Gardiner, N M; Couturier, C S; Stecyk, J A W; Nilsson, G E; Munday, P L; Rummer, J L

    2014-09-01

    Tropical regions are expected to be some of the most affected by rising sea surface temperatures (SSTs) because seasonal temperature variations are minimal. As temperatures rise, less oxygen dissolves in water, but metabolic requirements of fish and thus, the demand for effective oxygen uptake, increase. Gill remodelling is an acclimation strategy well documented in freshwater cyprinids experiencing large seasonal variations in temperature and oxygen as well as an amphibious killifish upon air exposure. However, no study has investigated whether tropical reef fishes remodel their gills to allow for increased oxygen demands at elevated temperatures. We tested for gill remodelling in five coral reef species (Acanthochromis polyacanthus, Chromis atripectoralis, Pomacentrus moluccensis, Dascyllus melanurus and Cheilodipterus quinquelineatus) from populations in northern Papua New Guinea (2° 35.765' S; 150° 46.193' E). Fishes were acclimated for 12-14 days to 29 and 31°C (representing their seasonal range) and 33 and 34°C to account for end-of-century predicted temperatures. We measured lamellar perimeter, cross-sectional area, base thickness, and length for five filaments on the 2nd gill arches and qualitatively assessed 3rd gill arches via scanning electron microscopy (SEM). All species exhibited significant differences in the quantitative measurements made on the lamellae, but no consistent trends with temperature were observed. SEM only revealed alterations in gill morphology in P. moluccensis. The overall lack of changes in gill morphology with increasing temperature suggests that these near-equatorial reef fishes may fail to maintain adequate O2 uptake under future climate scenarios unless other adaptive mechanisms are employed. PMID:24862962

  14. Localized corrosion testing of CRA materials in elevated temperature sour gas environments

    SciTech Connect

    Felton, P.; Oldfield, J.W.; Al-Maslamani, M.

    1999-11-01

    An exposure test program has been undertaken to investigate the localized corrosion resistance of Alloys 28, 825, G3 and 625 in two simulated sour gas environments at 150 C. The chloride levels in these test environments, containing 30 psi (0.21 MPa) H{sub 2}S and 101 psi (0.70 MPa) CO{sub 2}, were 150 ppm and 30,000 ppm. The general corrosion rate of each material was found to be negligible in each test. Alloy 825 alone was susceptible to minor pitting and crevice initiation in the 150 ppm chloride environment. Increasing the chloride level to 30,000 ppm resulted in more severe crevice attack of Alloy 825 and crevice corrosion of Alloy 28. Alloys G3 and 625 were not susceptible to localized corrosion in either test environment. The exposure tests were supported by complementary electrochemical polarization curves in the low chloride environment. The curves did not exhibit clearly defined passive regions, which were masked by additional anodic current from the oxidation of H{sub 2}S.

  15. Compatibility of strontium-90 fluoride with containment materials at elevated temperatures

    SciTech Connect

    Fullam, H.T.

    1981-08-01

    The use of /sup 90/SrF/sub 2/ as a heat-source fuel requires that the /sup 90/Sr be adequately contained during heat-source service. A program for determining the compatibility of /sup 90/SrF/sub 2/ with containment materials at heat-source operating temperatures is described. These compatibility studies included: initial and supplemental screening tests; WESF /sup 90/SrF/sub 2/ capsule demonstration tests; thermal gradient test; and long-term tests. TZM, Haynes Alloy 25, and Hastelloy C-276 were the three materitals selected for evaluation at 600/sup 0/, 800/sup 0/ and 1000/sup 0/C for periods up to 30,000 h. Results showed that all three alloys suffered substantial attack when exposed to the /sup 90/SrF/sub 2/, although the TZM was more resistant to attack than the Hastelloy C-276 and Haynes Alloy 25. The latter two alloys appeared to provide about equal resistance to fluoride attack for exposures longer than about 12,000 h. Attack of the alloys tested by the /sup 90/SrF/sub 2/ was due primarily to impurities.

  16. Studies on effects of elevated temperature for guided-wave structural health monitoring

    NASA Astrophysics Data System (ADS)

    Raghavan, Ajay; Cesnik, Carlos E. S.

    2007-04-01

    Large thermal variations can cause significant changes in guided-wave (GW) propagation and transduction for structural health monitoring (SHM). This work focuses on GW SHM using surface-bonded piezoelectric wafer transducers in metallic plates for the temperature range encountered in internal spacecraft structures (20°C to 150°C). First, studies done to determine a suitable bonding agent are documented. That was then used in controlled experiments to examine changes in GW propagation and transduction using PZT-5A piezoelectric wafers under quasi-statically varying temperature (also from 20°C to 150°C). Modeling efforts to explain the experimentally observed increase in time-of-flight and change in sensor response amplitude with increasing temperature are detailed. Finally, these results are used in detection and location of mild and moderate damage using the pulse-echo GW testing approach within the temperature range.

  17. Investigation of Problems Associated with the Use of Alloyed Molybdenum Sheet in Structures at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Mathauser, Eldon E.; Stein, Bland A.; Rummler, Donald R.

    1960-01-01

    The results of an experimental study to explore the capabilities and limitations of thin Mo-0.5Ti molybdenum-alloy sheet for structural applications at high temperatures are presented. Evaluation tests at temperatures ranging from room temperature,to 3000 F were made on resistance-welded corrugated-core sandwiches that were coated with a commercially available oxidation resistant coating known as W-2 and on coated oxidation and tensile specimens. The performance of the corrugated-core sandwiches in compressive strength and static oxidation tests, tensile properties of the coated molybdenum sheet, and the life of the coated specimens in static oxidation tests are given. A description of the equipment and procedures utilized in performing the evaluation tests is included.

  18. Experiments to study strain gage load calibrations on a wing structure at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Monaghan, R. C.; Fields, R. A.

    1973-01-01

    Laboratory experiments were performed to study changes in strain-gage bridge load calibrations on a wing structure heated to temperatures of 200 F, 400 F, and 600 F. Data were also obtained to define the experimental repeatability of strain-gage bridge outputs. Experiments were conducted to establish the validity of the superposition of bridge outputs due to thermal and mechanical loads during a heating simulation of Mach 3 flight. The strain-gage bridge outputs due to load cycle at each of the above temperature levels were very repeatable. A number of bridge calibrations were found to change significantly as a function of temperature. The sum of strain-gage bridge outputs due to individually applied thermal and mechanical loads compared well with that due to combined or superimposed loads. The validity of superposition was, therefore, established.

  19. Effect of elevated temperature on the composition, structure, and mechanical properties of diffusion chromized steel

    SciTech Connect

    Osintsev, V.D.

    1986-05-01

    The author studies the effect of operating temperature for equipment in contact sections of sulfuric acid workshops on the structure and mechanical properties of the chromized coatings and core of chromized articles. The ferrite lattice spacing was determined in a DRON-0.5 diffractometer according to the line in copper K /sub alpha/ radiation exposure was carried out after layer-by-layer anodic etching of the coating in an aqueous solution. It was shown that diffusion chromizing may lead to a reduction in strength properties compared with those of unchromized steel. As a base for chromized articles intended for operation at temperatures up to 475/sup 0/C it is desirable to use steels 09G2 or 09G25, or for operation at temperatures up to 540/sup 0/C, steels 12KhM and 12MKh.

  20. In situ soft XAS study on nickel-based layered cathode material at elevated temperatures: A novel approach to study thermal stability

    SciTech Connect

    Yoon, Won -Sub; Yang, Xiao -Qing; Haas, Otto; Muhammad, Shoaib; Kim, Hyunchul; Lee, Wontae; Kim, Donghwi; Fischer, Daniel A.; Jaye, Cherno; Balasubramanian, Mahalingam; Nam, Kyung -Wan

    2014-10-29

    Tracking thermally induced reactions has always been challenging for electrode materials of electrochemical battery systems. Traditionally, a variety of calorimetric techniques and in situ XRD at elevated temperatures has been used to evaluate the thermal stability of electrode materials. These techniques are capable of providing variations in heat capacity, mass and average bulk composition of materials only. Herein, we report investigation of thermal characteristics of Li0.33Ni0.8Co0.15Al0.05O2 by using in situ soft XAS measurements in combination with XRD. Fluorescence yield and partial electron yield measurements are used simultaneously to obtain element selective surface and bulk information. Fluorescence yield measurements reveal no energy change of the absorption peak and thus no valence state change in the bulk. However, electron yield measurements indicate that NiO-type rock salt structure is formed at the surface at temperatures above 200°C while no evidence for a surface reaction near Co sites in investigated temperature range is found. These results clearly show that in situ soft XAS can give a unique understanding of the role of each element in the structural transformation under thermal abuse offering a useful guidance in developing new battery system with improved safety performance.

  1. In situ soft XAS study on nickel-based layered cathode material at elevated temperatures: A novel approach to study thermal stability

    DOE PAGESBeta

    Yoon, Won -Sub; Yang, Xiao -Qing; Haas, Otto; Muhammad, Shoaib; Kim, Hyunchul; Lee, Wontae; Kim, Donghwi; Fischer, Daniel A.; Jaye, Cherno; Balasubramanian, Mahalingam; et al

    2014-10-29

    Tracking thermally induced reactions has always been challenging for electrode materials of electrochemical battery systems. Traditionally, a variety of calorimetric techniques and in situ XRD at elevated temperatures has been used to evaluate the thermal stability of electrode materials. These techniques are capable of providing variations in heat capacity, mass and average bulk composition of materials only. Herein, we report investigation of thermal characteristics of Li0.33Ni0.8Co0.15Al0.05O2 by using in situ soft XAS measurements in combination with XRD. Fluorescence yield and partial electron yield measurements are used simultaneously to obtain element selective surface and bulk information. Fluorescence yield measurements reveal nomore » energy change of the absorption peak and thus no valence state change in the bulk. However, electron yield measurements indicate that NiO-type rock salt structure is formed at the surface at temperatures above 200°C while no evidence for a surface reaction near Co sites in investigated temperature range is found. These results clearly show that in situ soft XAS can give a unique understanding of the role of each element in the structural transformation under thermal abuse offering a useful guidance in developing new battery system with improved safety performance.« less

  2. In situ soft XAS study on nickel-based layered cathode material at elevated temperatures: A novel approach to study thermal stability

    PubMed Central

    Yoon, Won-Sub; Haas, Otto; Muhammad, Shoaib; Kim, Hyunchul; Lee, Wontae; Kim, Donghwi; Fischer, Daniel A.; Jaye, Cherno; Yang, Xiao-Qing; Balasubramanian, Mahalingam; Nam, Kyung-Wan

    2014-01-01

    Tracking thermally induced reactions has always been challenging for electrode materials of electrochemical battery systems. Traditionally, a variety of calorimetric techniques and in situ XRD at elevated temperatures has been used to evaluate the thermal stability of electrode materials. These techniques are capable of providing variations in heat capacity, mass and average bulk composition of materials only. Herein, we report investigation of thermal characteristics of Li0.33Ni0.8Co0.15Al0.05O2 by using in situ soft XAS measurements in combination with XRD. Fluorescence yield and partial electron yield measurements are used simultaneously to obtain element selective surface and bulk information. Fluorescence yield measurements reveal no energy change of the absorption peak and thus no valence state change in the bulk. However, electron yield measurements indicate that NiO-type rock salt structure is formed at the surface at temperatures above 200°C while no evidence for a surface reaction near Co sites in investigated temperature range is found. These results clearly show that in situ soft XAS can give a unique understanding of the role of each element in the structural transformation under thermal abuse offering a useful guidance in developing new battery system with improved safety performance. PMID:25351344

  3. In situ soft XAS study on nickel-based layered cathode material at elevated temperatures: A novel approach to study thermal stability

    NASA Astrophysics Data System (ADS)

    Yoon, Won-Sub; Haas, Otto; Muhammad, Shoaib; Kim, Hyunchul; Lee, Wontae; Kim, Donghwi; Fischer, Daniel A.; Jaye, Cherno; Yang, Xiao-Qing; Balasubramanian, Mahalingam; Nam, Kyung-Wan

    2014-10-01

    Tracking thermally induced reactions has always been challenging for electrode materials of electrochemical battery systems. Traditionally, a variety of calorimetric techniques and in situ XRD at elevated temperatures has been used to evaluate the thermal stability of electrode materials. These techniques are capable of providing variations in heat capacity, mass and average bulk composition of materials only. Herein, we report investigation of thermal characteristics of Li0.33Ni0.8Co0.15Al0.05O2 by using in situ soft XAS measurements in combination with XRD. Fluorescence yield and partial electron yield measurements are used simultaneously to obtain element selective surface and bulk information. Fluorescence yield measurements reveal no energy change of the absorption peak and thus no valence state change in the bulk. However, electron yield measurements indicate that NiO-type rock salt structure is formed at the surface at temperatures above 200°C while no evidence for a surface reaction near Co sites in investigated temperature range is found. These results clearly show that in situ soft XAS can give a unique understanding of the role of each element in the structural transformation under thermal abuse offering a useful guidance in developing new battery system with improved safety performance.

  4. Effect of service exposure on fatigue crack propagation of Inconel 718 turbine disc material at elevated temperatures

    SciTech Connect

    Jeong, Dae-Ho; Choi, Myung-Je; Goto, Masahiro; Lee, Hong-Chul; Kim, Sangshik

    2014-09-15

    In this study, the fatigue crack propagation behavior of Inconel 718 turbine disc with different service times from 0 to 4229 h was investigated at 738 and 823 K. No notable change in microstructural features, other than the increase in grain size, was observed with increasing service time. With increasing service time from 0 to 4229 h, the fatigue crack propagation rates tended to increase, while the ΔK{sub th} value decreased, in low ΔK regime and lower Paris' regime at both testing temperatures. The fractographic observation using a scanning electron microscope suggested that the elevated temperature fatigue crack propagation mechanism of Inconel 718 changed from crystallographic cleavage mechanism to striation mechanism in the low ΔK regime, depending on the grain size. The fatigue crack propagation mechanism is proposed for the crack propagating through small and large grains in the low ΔK regime, and the fatigue crack propagation behavior of Inconel 718 with different service times at elevated temperatures is discussed. - Highlights: • The specimens were prepared from the Inconel 718 turbine disc used for 0 to 4229 h. • FCP rates were measured at 738 and 823 K. • The ΔK{sub th} values decreased with increasing service time. • The FCP behavior showed a strong correlation with the grain size of used turbine disc.

  5. Susceptibility of Lasioderma serricorne (F.)(Coleoptera: Anobiidae) life stages to elevated temperatures used during structural heat treatments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Heat treatment of food-processing facilities involves using elevated temperatures (46 to 60°C for 24 h) for management of stored-product insect pests. Heat treatment is a viable alternative in certain circumstances to the fumigant methyl bromide in certain situations, which is being phased out in t...

  6. Microstructure and Property Evolution in Advanced Cladding and Duct Materials Under Long-Term Irradiation at Elevated Temperature: Critical Experiments

    SciTech Connect

    Was, Gary; Jiao, Zhijie; Allen, Todd; Yang, Yong

    2013-12-20

    The in-service degradation of reactor core materials is related to underlying changes in the irradiated microstructure. During reactor operation, structural components and cladding experience displacement of atoms by collisions with neutrons at temperatures at which the radiation-induced defects are mobile, leading to microstructure evolution under irradiation that can degrade material properties. At the doses and temperatures relevant to fast reactor operation, the microstructure evolves by microchemistry changes due to radiation-induced segregation, dislocation loop formation and growth, radiation induced precipitation, destabilization of the existing precipitate structure, as well as the possibility for void formation and growth. These processes do not occur independently; rather, their evolution is highly interlinked. Radiation-induced segregation of Cr and existing chromium carbide coverage in irradiated alloy T91 track each other closely. The radiation-induced precipitation of Ni-Si precipitates and RIS of Ni and Si in alloys T91 and HCM12A are likely related. Neither the evolution of these processes nor their coupling is understood under the conditions required for materials performance in fast reactors (temperature range 300-600°C and doses to 200 dpa and beyond). Further, predictive modeling is not yet possible, as models for microstructure evolution must be developed along with experiments to characterize these key processes and provide tools for extrapolation. To extend the range of operation of nuclear fuel cladding and structural materials in advanced nuclear energy and transmutation systems to that required for the fast reactor, the irradiation-induced evolution of the microstructure, microchemistry, and the associated mechanical properties at relevant temperatures and doses must be understood. This project builds upon joint work at the proposing institutions, under a NERI-C program that is scheduled to end in September, to understand the effects of

  7. Characterization of microstructure and property evolution in advanced cladding and duct: Materials exposed to high dose and elevated temperature

    DOE PAGESBeta

    Allen, Todd R.; Kaoumi, Djamel; Wharry, Janelle P.; Jiao, Zhijie; Topbasi, Cem; Kohnert, Aaron; Barnard, Leland; Certain, Alicia; Field, Kevin G.; Was, Gary S.; et al

    2015-05-20

    Designing materials for performance in high-radiation fields can be accelerated through a carefully chosen combination of advanced multiscale modeling paired with appropriate experimental validation. Here, the studies reported in this work, the combined efforts of six universities working together as the Consortium on Cladding and Structural Materials, use that approach to focus on improving the scientific basis for the response of ferritic–martensitic steels to irradiation. A combination of modern modeling techniques with controlled experimentation has specifically focused on improving the understanding of radiation-induced segregation, precipitate formation and growth under radiation, the stability of oxide nanoclusters, and the development of dislocationmore » networks under radiation. Experimental studies use both model and commercial alloys, irradiated with both ion beams and neutrons. Lastly, transmission electron microscopy and atom probe are combined with both first-principles and rate theory approaches to advance the understanding of ferritic–martensitic steels.« less

  8. Characterization of microstructure and property evolution in advanced cladding and duct: Materials exposed to high dose and elevated temperature

    SciTech Connect

    Allen, Todd R.; Kaoumi, Djamel; Wharry, Janelle P.; Jiao, Zhijie; Topbasi, Cem; Kohnert, Aaron; Barnard, Leland; Certain, Alicia; Field, Kevin G.; Was, Gary S.; Morgan, Dane L.; Motta, Arthur T.; Wirth, Brian D.; Yang, Y.

    2015-05-20

    Designing materials for performance in high-radiation fields can be accelerated through a carefully chosen combination of advanced multiscale modeling paired with appropriate experimental validation. Here, the studies reported in this work, the combined efforts of six universities working together as the Consortium on Cladding and Structural Materials, use that approach to focus on improving the scientific basis for the response of ferritic–martensitic steels to irradiation. A combination of modern modeling techniques with controlled experimentation has specifically focused on improving the understanding of radiation-induced segregation, precipitate formation and growth under radiation, the stability of oxide nanoclusters, and the development of dislocation networks under radiation. Experimental studies use both model and commercial alloys, irradiated with both ion beams and neutrons. Lastly, transmission electron microscopy and atom probe are combined with both first-principles and rate theory approaches to advance the understanding of ferritic–martensitic steels.

  9. Superplastic forming and diffusion bonding of rapidly solidified, dispersion strengthened aluminum alloys for elevated temperature structural applications

    NASA Technical Reports Server (NTRS)

    Ting, E. Y.; Kennedy, J. R.

    1989-01-01

    Rapidly solidified alloys, based upon the Al-Fe-V-Si system and designed for elevated temperature applications, were evaluated for superplasticity and diffusion bonding behavior. Alloys with 8, 16, 27, and 36 volume percent silicide dispersoids were produced; dispersoid condition was varied by rolling at 300, 400, and 500 C (572, 752, and 932 F). Superplastic behavior was evaluated at strain rates from 1 x 10(exp -6)/s to 8.5/s at elevated temperatures. The results indicate that there was a significant increase in elongation at higher strain rates and at temperatures above 600 C (1112 F). However, the exposure of the alloys to temperatures greater than 600 C (1112 F) resulted in the coarsening of the strengthening dispersoid and the degradation of mechanical properties. Diffusion bonding was possible using low gas pressure at temperatures greater than 600 C (1112 F) which also resulted in degraded properties. The bonding of Al-Fe-V-Si alloys to 7475 aluminum alloy was performed at 516 C (960 F) without significant degradation in microstructure. Bond strengths equal to 90 percent that of the base metal shear strength were achieved. The mechanical properties and microstructural characteristics of the alloys were investigated.

  10. Elevated temperature fatigue testing of metals

    NASA Technical Reports Server (NTRS)

    Hirschberg, M. H.

    1981-01-01

    The major technology areas needed to perform a life prediction of an aircraft turbine engine hot section component are discussed and the steps required for life prediction are outlined. These include the determination of the operating environment, the calculation of the thermal and mechanical loading of the component, the cyclic stress-strain and creep behavior of the material required for structural analysis, and the structural analysis to determine the local stress-strain-temperature-time response of the material at the critical location in the components. From a knowledge of the fatigue, creep, and failure resistance of the material, a prediction of the life of the component is made. Material characterization and evaluation conducted for the purpose of calculating fatigue crack initiation lives of components operating at elevated temperatures are emphasized.

  11. Elevated temperature biaxial fatigue

    NASA Technical Reports Server (NTRS)

    Jordan, E. H.

    1984-01-01

    A three year experimental program for studying elevated temperature biaxial fatigue of a nickel based alloy Hastelloy-X has been completed. A new high temperature fatigue test facility with unique capabilities has been developed. Effort was directed toward understanding multiaxial fatigue and correlating the experimental data to the existing theories of fatigue failure. The difficult task of predicting fatigue lives for non-proportional loading was used as an ultimate test for various life prediction methods being considered. The primary means of reaching improved undertanding were through several critical non-proportional loading experiments. It was discovered that the cracking mode switched from primarily cracking on the maximum shear planes at room temperature to cracking on the maximum normal strain planes at 649 C.

  12. Elevated temperature crack growth

    NASA Technical Reports Server (NTRS)

    Kim, K. S.; Vanstone, R. H.

    1992-01-01

    The purpose of this program was to extend the work performed in the base program (CR 182247) into the regime of time-dependent crack growth under isothermal and thermal mechanical fatigue (TMF) loading, where creep deformation also influences the crack growth behavior. The investigation was performed in a two-year, six-task, combined experimental and analytical program. The path-independent integrals for application to time-dependent crack growth were critically reviewed. The crack growth was simulated using a finite element method. The path-independent integrals were computed from the results of finite-element analyses. The ability of these integrals to correlate experimental crack growth data were evaluated under various loading and temperature conditions. The results indicate that some of these integrals are viable parameters for crack growth prediction at elevated temperatures.

  13. Microstructure and Property Evolution in Advanced Cladding and Duct Materials Under Long-Term and Elevated Temperature Irradiation: Modeling and Experimental Investigation

    SciTech Connect

    Wirth, Brian; Morgan, Dane; Kaoumi, Djamel; Motta, Arthur

    2013-12-01

    irradiation. This project will focus on modeling microstructural and microchemical evolution of irradiated alloys by performing detailed modeling of such microstructure evolution processes coupled with well-designed in situ experiments that can provide validation and benchmarking to the computer codes. The broad scientific and technical objectives of this proposal are to evaluate the microstructure and microchemical evolution in advanced ferritic/martensitic and oxide dispersion strengthened (ODS) alloys for cladding and duct reactor materials under long-term and elevated temperature irradiation, leading to improved ability to model structural materials performance and lifetime. Specifically, we propose four research thrusts, namely Thrust 1: Identify the formation mechanism and evolution for dislocation loops with Burgers vector of a<100> and determine whether the defect microstructure (predominately dislocation loop/dislocation density) saturates at high dose. Thrust 2: Identify whether a threshold irradiation temperature or dose exists for the nucleation of growing voids that mark the beginning of irradiation-induced swelling, and begin to probe the limits of thermal stability of the tempered Martensitic structure under irradiation. Thrust 3: Evaluate the stability of nanometer sized Y- Ti-O based oxide dispersion strengthened (ODS) particles at high fluence/temperature. Thrust 4: Evaluate the extent to which precipitates form and/or dissolve as a function of irradiation temperature and dose, and how these changes are driven by radiation induced segregation and microchemical evolutions and determined by the initial microstructure.

  14. 1-3 connectivity composite material made from lithium niobate and cement for ultrasonic condition monitoring at elevated temperatures.

    PubMed

    Shepherd, G; Cochran, A; Kirk, K J; McNab, A

    2002-05-01

    We have designed, manufactured and tested a piezoelectric composite material to operate at temperatures above 400 degrees C. The material is a 1-3 connectivity composite with pillars of Z-cut lithium niobate in a matrix of alumina cement. The composite material produced shorter pulses than a monolithic plate of lithium niobate and remained intact upon cooling. Results are presented from room temperature and high temperature testing. This material could be bonded permanently to a test object, making it possible to carry out condition monitoring over an extended period. A new excitation method was also developed to enable remote switching between array elements. PMID:12159936

  15. Elevated temperature biaxial fatigue

    NASA Technical Reports Server (NTRS)

    Jordan, E. H.

    1985-01-01

    A 3 year experimental program for studying elevated temperature biaxial fatigue of a nickel based alloy Hastelloy-X has been completed. A new high temperature fatigue test facility with unique capabilities has been developed. Effort was directed toward understanding multiaxial fatigue and correlating the experimental data to the existing theories of fatigue failure. The difficult task of predicting fatigue lives for nonproportional loading was used as an ultimate test for various life prediction methods being considered. The primary means of reaching improved understanding were through several critical nonproportional loading experiments. The direction of cracking observed on failed specimens was also recorded and used to guide the development of the theory. Cyclic deformation responses were permanently recorded digitally during each test. It was discovered that the cracking mode switched from primarily cracking on the maximum shear planes at room temperature to cracking on the maximum normal strain planes at 649 C. In contrast to some other metals, loading path in nonproportional loading had little effect on fatigue lives. Strain rate had a small effect on fatigue lives at 649 C. Of the various correlating parameters the modified plastic work and octahedral shear stress were the most successful.

  16. Corrosion resistance and behavior of construction materials exposed to dilute sulfuric acid at elevated temperatures under static conditions

    SciTech Connect

    Nguyen, D.T.

    1994-10-01

    Laboratory investigation has been undertaken to determine the electrochemical behavior and corrosion resistance of various construction materials in a simulated hydrolysis environment (5 wt % sulfuric acid) at temperatures ranging from 90 to 220C. Tests were performed in an autoclave-type electrochemical cell. The corrosion behavior of the test materials was determined using computer-controlled DC potentiodynamic polarization. Corrosion rates of the test materials were determined using AC impedance techniques. Among the stainless steels tested, only alloy N08026 (Carpenter 20Mo-6) performed satisfactory up to a temperature of 100C. The alloy passivated spontaneously in the environment and corroded at a rate of less than 2 mpy. None of the stainless steels tested could be used at 120{degrees}C or above. A number of nickel-based alloys tested had good corrosion resistance up to 100C, but their corrosion rate exceeded 2 mpy at higher temperatures. Zirconium alloys were satisfactory up to 180C. Only tantalum and a tantalum-niobium alloy were satisfactory up to 220C.

  17. The mechanical properties of fluoride salts at elevated temperatures. [candidate thermal energy storage materials for solar dynamic systems

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Whittenberger, J. D.

    1989-01-01

    The deformation behavior of CaF2 and LiF single crystals compressed in the 111 and the 100 line directions, respectively, are compared with the mechanical properties of polycrystalline LiF-22 (mol pct) CaF2 eutectic mixture in the temperature range 300 to 1275 K for strain rates varying between 7 x 10 to the -7th and 0.2/s. The true stress-strain curves for the single crystals were found to exhibit three stages in an intermediate range of temperatures and strain rates, whereas those for the eutectic showed negative work-hardening rates after a maximum stress. The true stress-strain rate data for CaF2 and LiF-22 CaF2 could be represented by a power-law relation with the strain rate sensitivities lying between 0.05 and 0.2 for both materials. A similar relation was found to be unsatisfactory in the case of LiF.

  18. Combined effect of elevated UVB, elevated temperature and fertilization on growth, needle structure and phytochemistry of young Norway spruce (Picea abies) seedlings.

    PubMed

    Virjamo, Virpi; Sutinen, Sirkka; Julkunen-Tiitto, Riitta

    2014-07-01

    Simultaneously with warming climate, other climatic and environmental factors are also changing. Here, we investigated for the first time the effects of elevated temperature, increased ultraviolet-B (UVB) radiation, fertilization and all combinations of these on the growth, secondary chemistry and needle structure of 1-year-old Norway spruce (Picea abies (L.) Karst.) seedlings in an outdoor experiment. After one growing season, elevated temperature increased root : shoot ratio and concentrations of needle piperidine alkaloids, while concentrations of needle catechins and acetophenones and bark flavonoids decreased compared with ambient temperature seedlings. UVB-radiation increased concentrations of bark condensed tannins, while fertilization increased total biomass and concentrations of needle catechins. In addition to the main effects, concentrations of some individual phenolic compounds showed UV × temperature or UV × temperature × fertilization interactions, and fertilization modified temperature response on root : shoot ratio. All the treatments described here affected the defence chemistry profiles of the seedlings, which may imply some changes in plant-herbivore interactions in connection with changing climate. The interactions between treatments indicate a need for further experiments involving several simultaneously affecting environmental changes. PMID:24804850

  19. Elevated temperature strain gages

    NASA Technical Reports Server (NTRS)

    Brittain, J. O.; Geslin, D.; Lei, J. F.

    1986-01-01

    One of the goals of the HOST Program is the development of electrical resistance strain gages for static strain measurements at temperatures equal to or greater than 1273 K. Strain gage materials must have a reproducible or predictable response to temperature, time and strain. It is the objective of this research to investigate criteria for the selection of materials for such applications through electrical properties studies. The results of the investigation of two groups of materials, refractory compounds and binary alloy solid solutions are presented.

  20. Actinide Thermodynamics at Elevated Temperatures

    SciTech Connect

    Friese, Judah I.; Rao, Linfeng; Xia, Yuanxian; Bachelor, Paula P.; Tian, Guoxin

    2007-11-16

    The postclosure chemical environment in the proposed Yucca Mountain repository is expected to experience elevated temperatures. Predicting migration of actinides is possible if sufficient, reliable thermodynamic data on hydrolysis and complexation are available for these temperatures. Data are scarce and scattered for 25 degrees C, and nonexistent for elevated temperatures. This collaborative project between LBNL and PNNL collects thermodynamic data at elevated temperatures on actinide complexes with inorganic ligands that may be present in Yucca Mountain. The ligands include hydroxide, fluoride, sulfate, phosphate and carbonate. Thermodynamic parameters of complexation, including stability constants, enthalpy, entropy and heat capacity of complexation, are measured with a variety of techniques including solvent extraction, potentiometry, spectrophotometry and calorimetry

  1. Isochemical control over structural state and mechanical properties in Pd-based metallic glass by sputter deposition at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Magagnosc, Daniel J.; Feng, Gang; Yu, Le; Cheng, Xuemei; Gianola, Daniel S.

    2016-08-01

    Sputter deposition, while varying the substrate temperature, is employed to isochemically control the structural state and concomitant mechanical response in a Pd-based metallic glass at the time of glass formation. Increasing the deposition temperature from 333 K to 461 K results in a 33.5% increase in hardness to 9.69 GPa for amorphous films. Further increasing the temperature leads to a decrease in hardness, indicating low and high temperature deposition regimes where increased surface mobility allows access to a more relaxed and more rejuvenated structure, respectively. Through this mechanism we access the range of achievable structural states, from ultrastable to highly liquid-like glasses.

  2. Elevated temperature aluminum alloys

    NASA Technical Reports Server (NTRS)

    Meschter, Peter (Inventor); Lederich, Richard J. (Inventor); O'Neal, James E. (Inventor)

    1989-01-01

    Three aluminum-lithium alloys are provided for high performance aircraft structures and engines. All three alloys contain 3 wt % copper, 2 wt % lithium, 1 wt % magnesium, and 0.2 wt % zirconium. Alloy 1 has no further alloying elements. Alloy 2 has the addition of 1 wt % iron and 1 wt % nickel. Alloy 3 has the addition of 1.6 wt % chromium to the shared alloy composition of the three alloys. The balance of the three alloys, except for incidentql impurities, is aluminum. These alloys have low densities and improved strengths at temperatures up to 260.degree. C. for long periods of time.

  3. The development of gamma-gamma-prime lamellar structures in a nickel-base superalloy during elevated temperature mechanical testing

    NASA Technical Reports Server (NTRS)

    Mackay, R. A.; Ebert, L. J.

    1985-01-01

    The kinetics of the formation and subsequent development of the directional coarsening of the gamma-prime precipitate in model Ni-Al-Mo-Ta superalloy single crystals are examined during tensile creep under various stress levels at 982 and 1038 C. Special attention is given to the gamma and gamma-prime relation to creep time and strain in order to trace the changing gamma-gamma-prime morphology. Directional coarsening of gamma-prime is found to begin during primary creep and its rate is shown to increase with an increase in temperature or stress level. The length of gamma-prime thickness increased linearly with time up to a plateau reached after the onset of steady state creep. The raft thickness, equal to the gamma-prime size, remained constant at this initial value up through the onset of the tertiary creep. The interlaminar spacing indicates the stability of directionally coarsened structure.

  4. Effect of isomeric structures of branched cyclic hydrocarbons on densities and equation of state predictions at elevated temperatures and pressures.

    PubMed

    Wu, Yue; Bamgbade, Babatunde A; Burgess, Ward A; Tapriyal, Deepak; Baled, Hseen O; Enick, Robert M; McHugh, Mark A

    2013-07-25

    The cis and trans conformation of a branched cyclic hydrocarbon affects the packing and, hence, the density, exhibited by that compound. Reported here are density data for branched cyclohexane (C6) compounds including methylcyclohexane, ethylcyclohexane (ethylcC6), cis-1,2-dimethylcyclohexane (cis-1,2), cis-1,4-dimethylcyclohexane (cis-1,4), and trans-1,4-dimethylcyclohexane (trans-1,4) determined at temperatures up to 525 K and pressures up to 275 MPa. Of the four branched C6 isomers, cis-1,2 exhibits the largest densities and the smallest densities are exhibited by trans-1,4. The densities are modeled with the Peng-Robinson (PR) equation of state (EoS), the high-temperature, high-pressure, volume-translated (HTHP VT) PREoS, and the perturbed chain, statistical associating fluid theory (PC-SAFT) EoS. Model calculations highlight the capability of these equations to account for the different densities observed for the four isomers investigated in this study. The HTHP VT-PREoS provides modest improvements over the PREoS, but neither cubic EoS is capable of accounting for the effect of isomer structural differences on the observed densities. The PC-SAFT EoS, with pure component parameters from the literature or from a group contribution method, provides improved density predictions relative to those obtained with the PREoS or HTHP VT-PREoS. However, the PC-SAFT EoS, with either set of parameters, also cannot fully account for the effect of the C6 isomer structure on the resultant density. PMID:23815675

  5. Effect of Isomeric Structures of Branched Cyclic Hydrocarbons on Densities and Equation of State Predictions at Elevated Temperatures and Pressures

    SciTech Connect

    Wu, Yue; Bamgbade, Babatunde A; Burgess, Ward A; Tapriyal, Deepak; Baled, Hseen O; Enick, Robert M; McHugh, Mark

    2013-07-25

    The cis and trans conformation of a branched cyclic hydrocarbon affects the packing and, hence, the density, exhibited by that compound. Reported here are density data for branched cyclohexane (C6) compounds including methylcyclohexane, ethylcyclohexane (ethylcC6), cis-1,2-dimethylcyclohexane (cis-1,2), cis-1,4-dimethylcyclohexane (cis-1,4), and trans-1,4-dimethylcyclohexane (trans-1,4) determined at temperatures up to 525 K and pressures up to 275 MPa. Of the four branched C6 isomers, cis-1,2 exhibits the largest densities and the smallest densities are exhibited by trans-1,4. The densities are modeled with the Peng–Robinson (PR) equation of state (EoS), the high-temperature, high-pressure, volume-translated (HTHP VT) PREoS, and the perturbed chain, statistical associating fluid theory (PC-SAFT) EoS. Model calculations highlight the capability of these equations to account for the different densities observed for the four isomers investigated in this study. The HTHP VT-PREoS provides modest improvements over the PREoS, but neither cubic EoS is capable of accounting for the effect of isomer structural differences on the observed densities. The PC-SAFT EoS, with pure component parameters from the literature or from a group contribution method, provides improved density predictions relative to those obtained with the PREoS or HTHP VT-PREoS. However, the PC-SAFT EoS, with either set of parameters, also cannot fully account for the effect of the C6 isomer structure on the resultant density.

  6. Buffer strips in composites at elevated temperature

    NASA Technical Reports Server (NTRS)

    Bigelow, C. A.

    1983-01-01

    The composite material 'buffer strip' concept is presently investigated at elevated temperatures for the case of graphite/polyimide buffer strip panels using a (45/0/45/90)2S layup, where the buffer strip material was 0-deg S-glass/polyimide. Each panel was loaded in tension until it failed, and radiographs and crack opening displacements were recorded during the tests to determine fracture onset, fracture arrest, and the extent of damage in the buffer strip after crack arrest. At 177 + or - 3 C, the buffer strips increased the panel strength by at least 40 percent in comparison with panels without buffer strips. Compared to similar panels tested at room temperature, those tested at elevated temperature had lower residual strengths, but higher failure strains.

  7. Ion implantation at elevated temperatures

    SciTech Connect

    Lam, N.Q.; Leaf, G.K.

    1985-11-01

    A kinetic model has been developed to investigate the synergistic effects of radiation-enhanced diffusion, radiation-induced segregation and preferential sputtering on the spatial redistribution of implanted solutes during implantation at elevated temperatures. Sample calculations were performed for Al and Si ions implanted into Ni. With the present model, the influence of various implantation parameters on the evolution of implant concentration profiles could be examined in detail.

  8. Effect of Elevated CO2 Concentration, Elevated Temperature and No Nitrogen Fertilization on Methanogenic Archaeal and Methane-Oxidizing Bacterial Community Structures in Paddy Soil

    PubMed Central

    Liu, Dongyan; Tago, Kanako; Hayatsu, Masahito; Tokida, Takeshi; Sakai, Hidemitsu; Nakamura, Hirofumi; Usui, Yasuhiro; Hasegawa, Toshihiro; Asakawa, Susumu

    2016-01-01

    Elevated concentrations of atmospheric CO2 ([CO2]) enhance the production and emission of methane in paddy fields. In the present study, the effects of elevated [CO2], elevated temperature (ET), and no nitrogen fertilization (LN) on methanogenic archaeal and methane-oxidizing bacterial community structures in a free-air CO2 enrichment (FACE) experimental paddy field were investigated by PCR-DGGE and real-time quantitative PCR. Soil samples were collected from the upper and lower soil layers at the rice panicle initiation (PI) and mid-ripening (MR) stages. The composition of the methanogenic archaeal community in the upper and lower soil layers was not markedly affected by the elevated [CO2], ET, or LN condition. The abundance of the methanogenic archaeal community in the upper and lower soil layers was also not affected by elevated [CO2] or ET, but was significantly increased at the rice PI stage and significantly decreased by LN in the lower soil layer. In contrast, the composition of the methane-oxidizing bacterial community was affected by rice-growing stages in the upper soil layer. The abundance of methane-oxidizing bacteria was significantly decreased by elevated [CO2] and LN in both soil layers at the rice MR stage and by ET in the upper soil layer. The ratio of mcrA/pmoA genes correlated with methane emission from ambient and FACE paddy plots at the PI stage. These results indicate that the decrease observed in the abundance of methane-oxidizing bacteria was related to increased methane emission from the paddy field under the elevated [CO2], ET, and LN conditions. PMID:27600710

  9. Modeling of High-Strain-Rate Deformation, Fracture, and Impact Behavior of Advanced Gas Turbine Engine Materials at Low and Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Shazly, Mostafa; Nathenson, David; Prakash, Vikas

    2003-01-01

    Gamma titanium aluminides have received considerable attention over the last decade. These alloys are known to have low density, good high temperature strength retention, and good oxidation and corrosion resistance. However, poor ductility and low fracture toughness have been the key limiting factors in the full utilization of these alloys. More recently, Gamma-met PX has been developed by GKSS, Germany. These alloys have been observed to have superior strengths at elevated temperatures and quasi-static deformation rates and good oxidation resistance at elevated temperatures when compared with other gamma titanium aluminides. The present paper discusses results of a study to understand dynamic response of gamma-met PX in uniaxial compression. The experiments were conducted by using a modified split Hopkinson pressure bar between room temperature and 900 C and strain rates of up to 3500 per second. The Gamma met PX alloy showed superior strength when compared to nickel based superalloys and other gamma titanium aluminides at all test temperatures. It also showed strain and strain-rate hardening at all levels of strain rates and temperatures and without yield anomaly up to 900 C. After approximately 600 C, thermal softening is observed at all strain rates with the rate of thermal softening increasing dramatically between 800 and 900 C. However, these flow stress levels are comparatively higher in Gamma met PX than those observed for other TiAl alloys.

  10. Elevated-Temperature "Ultra" Fast Fracture Strength of Advanced Ceramics: An Approach to Elevated-Temperature "Inert" Strength

    NASA Technical Reports Server (NTRS)

    Choi, S. R.; Gyekenyesi, J. P.

    1999-01-01

    The determination of "ultra" fast fracture strengths of five silicon nitride ceramics at elevated temperatures has been made by using constant stress-rate ("dynamic fatigue") testing with a series of "ultra" fast test rates. The test material included four monolithic and one SiC whisker-reinforced composite silicon nitrides. Of the five test materials, four silicon nitrides exhibited the elevated -temperature strengths that approaches their respective room-temperature strengths at an "ultra" fast test rate of 3.3 x 10(exp 4) MPa/s. This implies that slow cracks growth responsible for elevated-temperature failure can be eliminated or minimized by using the "ultra" fast test rate. These ongoing experimental results have shed light on laying a theoretical and practical foundation on the concept and definition of elevated-temperature "inert" strength behavior of advanced ceramics.

  11. Monotonic and cyclic deformation behavior of a SiCw/6061 Al composite at elevated temperature

    SciTech Connect

    Wang, L.; Sun, Z.M.; Kobayashi, T.

    1996-10-15

    With the advent of new processing techniques, the technological interest and research activity in the development of metal-matrix composites have increased rapidly. Particularly, discontinuously reinforced composites, such as whisker and particle reinforced aluminum-based metal-matrix composites, exhibit attractive advantages, such as high specific modulus, high specific strength, good fatigue resistance and easy fabrication. They have emerged as a new class of structural materials for ambient and elevated temperature applications in aerospace and automobile industries. Therefore, great attention has been paid on their mechanical properties. However, a limited number of investigations on the cyclic deformation behavior have been reported, and little research has been done in this aspect at elevated temperature. The present study is based on a previous study at room temperature to investigate the monotonic and cyclic deformation behavior of a SiC whisker reinforced 6061 Al alloy composite and its unreinforced counterpart at elevated temperature.

  12. Electride-like phases at extreme compression and elevated temperatures

    NASA Astrophysics Data System (ADS)

    Bonev, Stanimir; Dubois, Jonathan

    The transformation of materials into electride-like structures under the application of extreme pressure has attracted a lot of interest recently. Theoretical studies have predicted the existence of low-coordinated crystal phases, where the conduction electrons are localized in the interstitial atomic regions, for a number of elements at high density. Most of these works have been limited to static lattice calculations. The pressures where such transformations are projected to occur are accessible in shock-wave experiments, but at elevated temperatures. In this talk I will discuss the temperature dependence of elecride structures, both solids and liquids, as well as the requirements for their accurate simulation. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  13. The Deformation-DIA: A Novel Apparatus for Measuring the Strength of Materials at High Strain to Pressures at Elevated Temperature

    SciTech Connect

    Durham, W

    2004-03-10

    The primary focus of this 3-year project was to develop and put to use an instrument to test experimentally the effect of pressure on body centered cubic (BCC) metals and other materials of interest to the Stockpile Stewardship program. Well-resolved materials testing requires measurements of load and deformation rate be measured at separable conditions of temperature, pressure, and plastic strain. The new apparatus at the heart of this work, the Deformation-DIA (D-DIA), began the project as a design concept. Its principal feature would be the capability to extend the conditions for such controlled materials testing from the current pressure limit of about 3 to almost 15 GPa, a factor of 5 increase. Once constructed and successfully tested, the plan of the project was to deform samples of BCC metals at arbitrary temperature and high pressures in order to provide preliminary measurements of strength and to prove its worth to the Stockpile Stewardship program. The project has been a stunning success. Progress toward demonstrating the worth of the D-DIA as a workhorse instrument for materials strength measurement at high pressure was given a huge boost by the fact that the machine itself functioned flawlessly from the very start, allowing the investigators to focus on measurement quality rather than technical operational issues. By the end of the project, we had deformed several samples of polycrystalline molybdenum (Mo) and tantalum (Ta) under very precisely controlled conditions, and for the Ta, had produced the first rudimentary measurements of strength to pressures of 8 GPa.

  14. Determination of Plate Compressive Strengths at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Heimerl, George J; Roberts, William M

    1950-01-01

    The results of local-instability tests of h-section plate assemblies and compressive stress-strain tests of extruded 75s-t6 aluminum alloy, obtained to determine flat-plate compressive strength under stabilized elevated temperature conditions, are given for temperatures up to 600 degrees F. The results show that methods available for calculating the critical compressive stress at room temperature can also be used at elevated temperatures if the applicable compressive stress-strain curve for the material is given.

  15. Properties of yttria-tetragonal zirconia polycrystal (Y-TZP) materials after long-term exposure to elevated temperatures. Final report

    SciTech Connect

    Swab, J.J.

    1989-03-01

    Seven commercially available yttria-tetragonal zirconia polycrystal (Y-TZP) materials were evaluated. Room temperature properties were measured before and after heat treatments at 1000C. Microstructure and phase stability were also examined. In all but one case, the Y-TZPs showed very little change in room temperature properties after long times at this temperature. Results show that pressure-assisted processing greatly improves the strength by reducing porosity and keeping the grain size extremely fine, but this reduces the toughness because finer grains are more difficult to transform. In addition, a small amount of cubic zirconia appears to enhance the toughness of fine-grained Y-TZP while maintaining good strength. During processing, a small amount of cubic zirconia is formed and allowed to grow. This creates regions poor in yttria which can transform spontaneously in the presence of a crack-tip stress field.

  16. Structure and properties of La-modified Na0.5Bi0.5TiO3 at ambient and elevated temperatures

    NASA Astrophysics Data System (ADS)

    Aksel, Elena; Forrester, Jennifer S.; Foronda, Humberto M.; Dittmer, Robert; Damjanovic, Dragan; Jones, Jacob L.

    2012-09-01

    The crystal structure and property changes of sodium bismuth titanate (Na0.5Bi0.5TiO3, NBT) piezoelectric ceramics are reported as a function of La modification (0.5-2.0 at. %) and increasing temperature using high resolution x-ray diffraction, permittivity, depolarization, and polarization and strain hysteresis measurements. La substitution is found to decrease the depolarization temperature of NBT (e.g., 1.5 at. % La substitution lowers the depolarization temperature by 60 °C relative to the unmodified composition) with little impact on the room temperature polarization and strain hysteresis. The room temperature structures of the various NBT compositions were modeled using a mixture of the monoclinic Cc space group and the cubic Pm3¯m phase, where the Pm3¯m phase is used to model local regions in the material which do not obey the long range Cc space group. With increasing La substitution, the lattice parameter distortions associated with the Cc phase approached that of the prototypical cubic unit cell and the fraction of the Pm3¯m phase increased. The relationship between these crystallographic changes and the depolarization behavior of La-modified NBT is discussed.

  17. A Study of Advanced Materials for Gas Turbine Coatings at Elevated Temperatures Using Selected Microstructures and Characteristic Environments for Syngas Combustion

    SciTech Connect

    Ravinder Diwan; Patrick Mensah; Guoqiang Li; Nalini Uppu; Strphen Akwaboa; Monica Silva; Ebubekir Beyazoglu; Ogad Agu; Naresh Polasa; Lawrence Bazille; Douglas Wolfe; Purush Sahoo

    2011-02-10

    Thermal barrier coatings (TBCs) that can be suitable for use in industrial gas turbine engines have been processed and compared with electron beam physical vapor deposition (EBPVD) microstructures for applications in advanced gas turbines that use coal-derived synthesis gas. Thermo-physical properties have been evaluated of the processed air plasma sprayed TBCs with standard APS-STD and vertically cracked APS-VC coatings samples up to 1300 C. Porosity of these selected coatings with related microstructural effects have been analyzed in this study. Wet and dry thermal cycling studies at 1125 C and spalling resistance thermal cycling studies to 1200 C have also been carried out. Type I and Type II hot corrosion tests were carried out to investigate the effects of microstructure variations and additions of alumina in YSZ top coats in multi-layered TBC structures. The thermal modeling of turbine blade has also been carried out that gives the capability to predict in-service performance temperature gradients. In addition to isothermal high temperature oxidation kinetics analysis in YSZ thermal barrier coatings of NiCoCrAlY bond coats with 0.25% Hf. This can affect the failure behavior depending on the control of the thermally grown oxide (TGO) growth at the interface. The TGO growth kinetics is seen to be parabolic and the activation energies correspond to interfacial growth kinetics that is controlled by the diffusion of O{sub 2} in Al{sub 2}O{sub 3}. The difference between oxidation behavior of the VC and STD structures are attributed to the effects of microstructure morphology and porosity on oxygen ingression into the zirconia and TGO layers. The isothermal oxidation resistance of the STD and VC microstructures is similar at temperatures up to 1200 C. However, the generally thicker TGO layer thicknesses and the slightly faster oxidation rates in the VC microstructures are attributed to the increased ingression of oxygen through the grain boundaries of the vertically

  18. Failure of welds at elevated temperatures

    SciTech Connect

    Stevick, G.R. )

    1994-04-01

    This thesis presents several new insights into creep crack growth problems: (1) the potential for stress concentrations resulting from the mismatch of creep properties between weld and base metals, (2) a creep crack growth model that includes the effects of stress triaxiality, and (3) a crack initiation model based on the statistical distribution of inclusion size and spacing. Longitudinally welded piping is used extensively in the power industry for high temperature applications. An elastic-creep finite element analysis of a typical symmetric, double-V longitudinal weld shows that a material stress concentration will develop in 1--2 years if creep properties of the weld and base metals are different. The stress concentration in the weld peaks mid-wall at the weld fusion line on both sides for the typical case in which creep strain rate of the weld metal is greater than that of the base metal. Finite element analysis results also showed that differences in material properties have a significant effect on the stress field after a crack has formed. The increased stress helps explain recent premature failures of longitudinally welded pipe in the power industry and suggest that the weld efficiency factors permitted by the ASME/ANSI B31.1 Piping Code should be reevaluated for longitudinal pipe welds at elevated temperatures.

  19. An experimental investigation into the behavior of glassfiber reinforced polymer elements at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Qian, Kenny Zongxi

    This thesis presents a literature review and results of an experimental study about the effects of high temperatures and cyclic loading on the physical and mechanical properties of pultruded glass fiber reinforced polymer (GFRP) square tubes used in civil engineering structural applications. Most laboratory researches have focused mainly on the effect of elevated temperature on the compressive strength of the GFRP square tubes. Limited research has focused on the tensile strength of GFRP coupons under elevated temperatures. Dynamic Mechanical Analyses (DMA) was performed to assess the viscoelastic behavior including the glass transition temperature of GFRP. Sixteen GFRP coupons were tested under elevated temperatures to investigate the tensile strength and the effect of elevated temperatures to the tensile strength of GFRP. The results of an experimental program performed on fifty GFRP square tubes with different designs in 1.83m at normal temperatures were discussed to investigate compression performance. Another experimental program was performed on 20 GFRP square tubes with different designs in 1.22m under elevated temperatures. The experiments results were discussed and showed that the compressive strength of GFRP material was influenced by several factors including the glass transition v temperature and the connection bolts. Failure modes under 25°C and 75°C were crushing and the failure modes with the temperatures above 75°C were not typical crushing due to the glass transition of GFRP. Sixteen GFRP square tubes with length of 0.61m were tested with the same experimental program under elevated temperatures as the control group. Twelve GFRP square tubes with the same size were subjected to cyclic loading under elevated temperatures to investigate the effect of the cyclic loading to the compression properties of GFRP material. According to the experimental results and the discussion, the stiffness was reduced by the cyclic loading. On the contrary, the

  20. Performance Evaluation of Fiber Bragg Gratings at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Juergens, Jeffrey; Adamovsky, Grigory; Floyd, Bertram

    2004-01-01

    The development of integrated fiber optic sensors for smart propulsion systems demands that the sensors be able to perform in extreme environments. In order to use fiber optic sensors effectively in an extreme environment one must have a thorough understanding of the sensor s limits and how it responds under various environmental conditions. The sensor evaluation currently involves examining the performance of fiber Bragg gratings at elevated temperatures. Fiber Bragg gratings (FBG) are periodic variations of the refractive index of an optical fiber. These periodic variations allow the FBG to act as an embedded optical filter passing the majority of light propagating through a fiber while reflecting back a narrow band of the incident light. The peak reflected wavelength of the FBG is known as the Bragg wavelength. Since the period and width of the refractive index variation in the fiber determines the wavelengths that are transmitted and reflected by the grating, any force acting on the fiber that alters the physical structure of the grating will change what wavelengths are transmitted and what wavelengths are reflected by the grating. Both thermal and mechanical forces acting on the grating will alter its physical characteristics allowing the FBG sensor to detect both temperature variations and physical stresses, strain, placed upon it. This ability to sense multiple physical forces makes the FBG a versatile sensor. This paper reports on test results of the performance of FBGs at elevated temperatures. The gratings looked at thus far have been either embedded in polymer matrix materials or freestanding with the primary focus of this paper being on the freestanding FBGs. Throughout the evaluation process, various parameters of the FBGs performance were monitored and recorded. These parameters include the peak Bragg wavelength, the power of the Bragg wavelength, and total power returned by the FBG. Several test samples were subjected to identical test conditions to

  1. Apparatus for elevated temperature compression or tension testing of specimens

    NASA Astrophysics Data System (ADS)

    Gates, Thomas S.

    1992-05-01

    In order to support materials selection for the next generation supersonic civilian passenger transport aircraft, a testing apparatus was developed to evaluate certain materials under conditions of high load and elevated temperature. In order to elevate the temperature of the material during standard tension and compression testing the test specimen is surrounded by a pair of supports which include internal heating means. These supports also prevent buckling of the specimen during compression testing.

  2. Viscoelastoplastic Deformation and Damage Response of Titanium Alloy, Ti-6Al-4V, at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Arnold, Steven M.; Lerch, Bradley A.; Saleeb, Atef F.; Kasemer, Matthew P.

    2013-01-01

    Time-dependent deformation and damage behavior can significantly affect the life of aerospace propulsion components. Consequently, one needs an accurate constitutive model that can represent both reversible and irreversible behavior under multiaxial loading conditions. This paper details the characterization and utilization of a multi-mechanism constitutive model of the GVIPS class (Generalized Viscoplastic with Potential Structure) that has been extended to describe the viscoelastoplastic deformation and damage of the titanium alloy Ti-6Al-4V. Associated material constants were characterized at five elevated temperatures where viscoelastoplastic behavior was observed, and at three elevated temperatures where damage (of both the stiffness reduction and strength reduction type) was incurred. Experimental data from a wide variety of uniaxial load cases were used to correlate and validate the proposed GVIPS model. Presented are the optimized material parameters, and the viscoelastoplastic deformation and damage responses at the various temperatures.

  3. Constitutive Modeling and Testing of Polymer Matrix Composites Incorporating Physical Aging at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Veazie, David R.

    1998-01-01

    Advanced polymer matrix composites (PMC's) are desirable for structural materials in diverse applications such as aircraft, civil infrastructure and biomedical implants because of their improved strength-to-weight and stiffness-to-weight ratios. For example, the next generation military and commercial aircraft requires applications for high strength, low weight structural components subjected to elevated temperatures. A possible disadvantage of polymer-based composites is that the physical and mechanical properties of the matrix often change significantly over time due to the exposure of elevated temperatures and environmental factors. For design, long term exposure (i.e. aging) of PMC's must be accounted for through constitutive models in order to accurately assess the effects of aging on performance, crack initiation and remaining life. One particular aspect of this aging process, physical aging, is considered in this research.

  4. Evaluation of components on a ductwork system at elevated temperatures

    SciTech Connect

    Shen, J.K.; Chern, C.Y.

    1995-12-31

    This paper evaluates the adequacy of a Deactivation Furnace System (DFS) for operation at elevated temperatures (from 1,100 F to 1,800 F). The piping components included in this evaluation are ductwork, flanges, expansion joints, duct support structures, bolts and other load bearing elements. The DFS is designed in accordance with ANSI/ASME B31.1 and B31.3 Codes. However, for the evaluations of elevated temperature conditions, ASME III Code Case N-253-6, Construction of Class 2 or Class 3 components for Elevated Temperature Service, and Code Case N-47-28, Class 1 components in Elevated Temperature Service, are used. To consider creep effects, the primary membrane stresses of piping components are calculated and compared with the stress to rupture based on the duration of operation temperature. The primary-membrane-plus-bending stresses are calculated to determine the use-fraction sum due to service loadings. If the calculated use-fraction sum of a component should exceed the allowable, the limited useful life could be predicted.

  5. Application of non-porous alumina based ceramics as structural material for devices handling tritium at elevated temperatures

    SciTech Connect

    Yukhimchuk, A.A.; Maksimkin, I.P.; Baluev, V.V.; Boitsov, I.E.; Vertey, A.V.; Malkov, I.L.; Musyaev, R.K.; Popov, V.V.; Sitdikov, D.T.; Khapov, A.S.; Grishechkin, S.K.; Kiselev, V.G.

    2015-03-15

    The article presents results of comparative tests for the determination of deuterium fluxes permeating through walls of austenitic stainless steel AISI304 (DIN 1.4301) chamber and Al{sub 2}O{sub 3} based ceramic F99.7 chamber. Both chambers represent a piece of φ(ext)=26*φ(int)=22*117 mm{sup 3} tube with spherical bottom ending. It is shown that at 773 K and deuterium pressure of 1200 mbar the permeated deuterium flux through the stainless steel chamber constituted 8*10{sup -5} cm{sup 3}/s, while the flux through ceramic one it did not exceed the sensitivity of the measurement method threshold, namely about 1.5*10{sup -7} cm{sup 3}/s. The ceramic chamber turned out to survive more than 10{sup 3} cycles of heating up to 773 K with no damages. It did not lose its tightness up to 10 bar of internal deuterium pressure. The authors also present test results of a prototype bed for reversible tritium storage. The bed's case was made of alumina based ceramic F99.7, titanium being used as tritide making metal and high frequency induction used for heating the tritide metal. (authors)

  6. Binder/HMX Interaction in PBX9501 at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Saw, Cheng K.; Tarver, Craig M.

    2004-07-01

    Plastic bonded explosives (PBX) generally consist of 85-95 % by weight energetic material, such as HMX, and 5-15 % polymeric binder. Understanding of the structure and morphology at elevated temperatures and pressures is important for predicting of PBX behavior in accident scenarios. The crystallographic behavior of pure HMX has been measured as functions of temperature and grain size. The investigation is extended to the high temperature behavior of PBX 9501 (95% HMX, 2.5 % Estane, 2.5 % BDNPA/F). The results show that the HMX β- to δ-phase transition in PBX 9501 is similar to that in neat HMX. However, in the presence of the PBX 9501 binder, δ-phase HMX readily converts back to β-phase during cooling. Using the same temperature profile, the conversion rate decreases for each subsequent heating and cooling cycle. As observed in earlier experiments, no reverse conversion is observed without the polymer binder. It is proposed that the reversion of δ-phase to β-phase is due to changes in the surface molecular potential caused by the influence of the polymer binder on the δ-phase. Upon thermal cycling, the polymer binder segregates from the HMX particles and thus reduces the influence of the binder on the surface molecules. This segregation increases the resistance for the δ-phase to β-phase transition, as demonstrated in an aged PBX 9501 material for which the reversion is not observed.

  7. Thermodynamics, Diffusion, and Structure of Liquid NaAlSi3O8 at Elevated Temperature and Pressure from Molecular Dynamics Simulations

    NASA Astrophysics Data System (ADS)

    Neilson, R.; Spera, F. J.; Ghiorso, M. S.

    2014-12-01

    Thermodynamic properties of silicate melts at high temperature (T) and pressure (P) are crucial to understanding Earth accretion, magma oceans, petrogenesis, and crustal growth. However, equations of state for silicate liquids at mantle conditions are scarce, due to experimental challenges. Molecular Dynamics (MD) simulations allow investigation of thermodynamic and transport properties of silicate melts at high P and T and enable the correlation of liquid structure with computed properties. Using classical MD, we studied liquid NaAlSi3O8 in the range 0-42 GPa and 3000-5137 K. Density ranged from 2.2 to 3.6 g/cm3, and all simulations were performed in the microcanonical (NEV) ensemble using the potential from Matsui (1998). An equation of state with internal energy E(V,T) was developed using the RT scaling-Vinet formulation (Ghiorso et al., 2009). From thermodynamic relationships, the Grüneisen parameter, isobaric expansivity, isothermal compressibility, heat capacity, and other functions are computed over the P-T range of the MD simulations. Diffusion coefficients (D) range from 1.5×10-9 to 5.9×10-8 m2/s and typically order Na>Al>O>Si at a given state point. Generally, D decreases with P and increases with T except for a low P anomalous region along the 3065 K isotherm. Anomalous diffusion for Al, Si, and O is congruent with laboratory experiments at P<10 GPa (e.g., Shimizu and Kushiro, 1984; Poe et al., 1997; Tinker and Lesher, 2001; Tinker et al., 2003). Activation energy for Na is on the order of -75.3 kJ/mol with activation volume -1.74 cm3/mol. The anomalous peak in diffusivity for Si and O occurs at ~3 GPa, which marks a subtle increase in the average coordination number (CN) for O around O from 9.35 to 10.31. The average CN for O around O generally increases with P, but it systematically drops at 8, 15, and 20 GPa for 3065, 3944, and 5137 K, respectively. The concentrations of AlO5 and SiO5 polyhedra maximize near 16 and 35 GPa, respectively.

  8. Friction Tests in Magnesium Tube Hydroforming at Elevated Temperatures

    SciTech Connect

    Hwang, Yeong-Maw; Wang, Kuo-Hsing; Kuo, Tsung-Yu

    2011-05-04

    In metal forming, lubricants have a variety of functions. The top priority is usually reduction of friction in order to increase the formability of the materials and reduce tool wear. Because magnesium alloys have very poor formability at room temperature, it is essential to manufacture a part from Magnesium alloys at elevated temperatures. The aim of this paper is to present a friction test method to evaluate the performance of different kinds of lubricants and determine their coefficients of friction at elevated temperatures in tube hydroforming of magnesium alloys. A self-designed experimental apparatus is used to carry out the experiments of friction tests. The coefficient of friction between the tube and die at guiding zone is determined. The effects of the internal pressure, the axial feeding velocity and temperatures on the friction forces and coefficients of friction for different lubricants are discussed.

  9. Void evolution in polycarbonate at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Chen, Y. H.; Feng Chou, Kuo; Li, C. L.; Lee, Sanboh

    2011-08-01

    The void evolution in polycarbonate (PC) at elevated temperatures was investigated. Internal cylindrical cracks and voids were induced in PC by Nd-YAG laser irradiation. During the annealing at temperatures of 177-197 °C, the spherical void grows to a maximum size, which then decreases, and is finally leveling off. A model of void evolution based on the evaporation and condensation mechanisms for growth and shrinkage is proposed. The theoretical predictions are in good agreement with the experimental data. The activation energies of evaporation and condensation processes are determined to be 477.31 and 611.49 kJ/mol, respectively.

  10. Gas-Alloy Interactions at Elevated Temperatures

    SciTech Connect

    Arroyave, Raymundo; Gao, Michael

    2012-11-07

    The understanding of the stability of metals and alloys against oxidation and other detrimental reactions, to the catalysis of important chemical reactions and the minimization of defects associated with processing and synthesis have one thing in common: At the most fundamental level, all these scientific/engineering problems involve interactions between metals and alloys (in the solid or liquid state) and gaseous atmospheres at elevated temperatures. In this special issue, we have collected a series of articles that illustrate the application of different theoretical, computational, and experimental techniques to investigate gas-alloy interactions.

  11. Void evolution in polycarbonate at elevated temperatures

    SciTech Connect

    Chen, Y. H.; Li, C. L.; Lee, Sanboh; Kuo Feng Chou

    2011-08-15

    The void evolution in polycarbonate (PC) at elevated temperatures was investigated. Internal cylindrical cracks and voids were induced in PC by Nd-YAG laser irradiation. During the annealing at temperatures of 177-197 deg. C, the spherical void grows to a maximum size, which then decreases, and is finally leveling off. A model of void evolution based on the evaporation and condensation mechanisms for growth and shrinkage is proposed. The theoretical predictions are in good agreement with the experimental data. The activation energies of evaporation and condensation processes are determined to be 477.31 and 611.49 kJ/mol, respectively.

  12. A statistical study on tensile characteristics of stainless steel at elevated temperatures

    NASA Astrophysics Data System (ADS)

    SungHo, Park; NoSeok, Park; JaeHoon, Kim

    2010-07-01

    This study describes the tensile test results of AISI type 304 deformed at room and elevated temperatures. It has been known that the normal distribution fits well with the strength of typical structural materials. The Weibull distribution has many characteristics in the reliability design. In this paper, we showed that the Weibull distribution can be used to describe the scattering of strength data as well as normal distribution by testing goodness of fit. It is found that the parameters of Weibull distribution have decreasing tendency for temperature rise and the coefficient of variation has increasing tendency for temperature rise.

  13. Ultrahigh pressure liquid chromatography using elevated temperature.

    PubMed

    Xiang, Yanqiao; Liu, Yansheng; Lee, Milton L

    2006-02-01

    Fast liquid chromatographic (LC) methods are important for a variety of applications. Reducing the particle diameter (d(p)) is the most effective way to achieve fast separations while preserving high efficiency. Since the pressure drop along a packed column is inversely proportional to the square of the particle size, when columns packed with small particles (<2 microm) are used, ultrahigh pressures (>689 bar) must be applied to overcome the resistance to mobile phase flow. Elevating the column temperature can significantly reduce the mobile phase viscosity, allowing operation at higher flow rate for the same pressure. It also leads to a decrease in retention factor. The advantage of using elevated temperatures in LC is the ability to significantly shorten separation time with minimal loss in column efficiency. Therefore, combining elevated temperature with ultrahigh pressure facilitates fast and efficient separations. In this study, C6-modified 1.0 microm nonporous silica particles were used to demonstrate fast separations using a temperature of 80 degrees C and a pressure of 2413 bar. Selected separations were completed in 30 s with efficiencies as high as 220,000 plates m(-1). PMID:16376355

  14. Elevated temperature strength of Cr-W alloys

    SciTech Connect

    Dogan, Omer N.; Schrems, Karol K.

    2004-09-01

    Cr alloys containing 0-30 weight percent W were investigated for their strength and ductility. These experimental alloys are intended for use in elevated temperature applications. Alloys were melted in a water-cooled, copper-hearth arc furnace. Microstructure of the alloys was studied using X-ray diffraction, scanning electron microscopy, and light microscopy. A hot hardness tester was used to study the strength of these materials up to 1200ºC. Compression tests at the same temperature range were also conducted.

  15. Elevated temperature forming method and preheater apparatus

    DOEpatents

    Krajewski, Paul E; Hammar, Richard Harry; Singh, Jugraj; Cedar, Dennis; Friedman, Peter A; Luo, Yingbing

    2013-06-11

    An elevated temperature forming system in which a sheet metal workpiece is provided in a first stage position of a multi-stage pre-heater, is heated to a first stage temperature lower than a desired pre-heat temperature, is moved to a final stage position where it is heated to a desired final stage temperature, is transferred to a forming press, and is formed by the forming press. The preheater includes upper and lower platens that transfer heat into workpieces disposed between the platens. A shim spaces the upper platen from the lower platen by a distance greater than a thickness of the workpieces to be heated by the platens and less than a distance at which the upper platen would require an undesirably high input of energy to effectively heat the workpiece without being pressed into contact with the workpiece.

  16. Promoted Metals Combustion at Ambient and Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Engel, Carl D.; Herald, Stephen D.; Davis, S. Eddie

    2005-01-01

    Promoted combustion testing of materials, Test 17 of NASA STD-6001, has been used to assess metal propensity to burn in oxygen rich environments. An igniter is used at the bottom end of a rod to promote ignition, and if combustion is sustained, the burning progresses from the bottom to the top of the rod. The physical mechanisms are very similar to the upward flammability test, Test 1 of NASA STD-6001. The differences are in the normal environmental range of pressures, oxygen content, and sample geometry. Upward flammability testing of organic materials can exhibit a significant transitional region between no burning to complete quasi-state burning. In this transitional region, the burn process exhibits a probabilistic nature. This transitional region has been identified for metals using the promoted combustion testing method at ambient initial temperatures. The work given here is focused on examining the transitional region and the quasi-steady burning region both at conventional ambient testing conditions and at elevated temperatures. A new heated promoted combustion facility and equipment at Marshall Space Flight Center have just been completed to provide the basic data regarding the metals operating temperature limits in contact with oxygen rich atmospheres at high pressures. Initial data have been obtained for Stainless Steel 304L, Stainless Steel 321, Haynes 214, and Inconel 718 at elevated temperatures in 100-percent oxygen atmospheres. These data along with an extended data set at ambient initial temperature test conditions are examined. The pressure boundaries of acceptable, non-burning usage is found to be lowered at elevated temperature.

  17. Elevated temperature deformation of thoria dispersed nickel-chromium

    NASA Technical Reports Server (NTRS)

    Kane, R. D.; Ebert, L. J.

    1974-01-01

    The deformation behavior of thoria nickel-chromium (TD-NiCr) was examined over the temperature range 593 C (1100 F) to 1260 C (2300 F) in tension and compression and at 1093 C (2000 F) in creep. Major emphasis was placed on: (1) the effects of the material and test related variables (grain size, temperature, stress and strain rate) on the deformation process; and (2) the evaluation of single crystal TD-NiCr material produced by a directional recrystallization process. Elevated temperature yield strength levels and creep activation enthalpies were found to increase with increasing grain size reaching maximum values for the single crystal TD-NiCr. Stress exponent of the steady state creep rate was also significantly higher for the single crystal TD-NiCr as compared to that determined for the polycrystalline materials. The elevated temperature deformation of TD-NiCr was analyzed in terms of two concurrent, parallel processes: diffusion controlled grain boundary sliding, and dislocation motion.

  18. High strain rate behavior of pure metals at elevated temperature

    NASA Astrophysics Data System (ADS)

    Testa, Gabriel; Bonora, Nicola; Ruggiero, Andrew; Iannitti, Gianluca; Domenico, Gentile

    2013-06-01

    In many applications and technology processes, such as stamping, forging, hot working etc., metals and alloys are subjected to elevated temperature and high strain rate deformation process. Characterization tests, such as quasistatic and dynamic tension or compression test, and validation tests, such as Taylor impact and DTE - dynamic tensile extrusion -, provide the experimental base of data for constitutive model validation and material parameters identification. Testing material at high strain rate and temperature requires dedicated equipment. In this work, both tensile Hopkinson bar and light gas gun where modified in order to allow material testing under sample controlled temperature conditions. Dynamic tension tests and Taylor impact tests, at different temperatures, on high purity copper (99.98%), tungsten (99.95%) and 316L stainless steel were performed. The accuracy of several constitutive models (Johnson and Cook, Zerilli-Armstrong, etc.) in predicting the observed material response was verified by means of extensive finite element analysis (FEA).

  19. Thermal Behavior of Cylindrical Buckling Restrained Braces at Elevated Temperatures

    PubMed Central

    Talebi, Elnaz; Tahir, Mahmood Md.; Yasreen, Airil

    2014-01-01

    The primary focus of this investigation was to analyze sequentially coupled nonlinear thermal stress, using a three-dimensional model. It was meant to shed light on the behavior of Buckling Restraint Brace (BRB) elements with circular cross section, at elevated temperature. Such bracing systems were comprised of a cylindrical steel core encased in a strong concrete-filled steel hollow casing. A debonding agent was rubbed on the core's surface to avoid shear stress transition to the restraining system. The numerical model was verified by the analytical solutions developed by the other researchers. Performance of BRB system under seismic loading at ambient temperature has been well documented. However, its performance in case of fire has yet to be explored. This study showed that the failure of brace may be attributed to material strength reduction and high compressive forces, both due to temperature rise. Furthermore, limiting temperatures in the linear behavior of steel casing and concrete in BRB element for both numerical and analytical simulations were about 196°C and 225°C, respectively. Finally it is concluded that the performance of BRB at elevated temperatures was the same as that seen at room temperature; that is, the steel core yields prior to the restraining system. PMID:24526915

  20. Thermal behavior of cylindrical buckling restrained braces at elevated temperatures.

    PubMed

    Talebi, Elnaz; Tahir, Mahmood Md; Zahmatkesh, Farshad; Yasreen, Airil; Mirza, Jahangir

    2014-01-01

    The primary focus of this investigation was to analyze sequentially coupled nonlinear thermal stress, using a three-dimensional model. It was meant to shed light on the behavior of Buckling Restraint Brace (BRB) elements with circular cross section, at elevated temperature. Such bracing systems were comprised of a cylindrical steel core encased in a strong concrete-filled steel hollow casing. A debonding agent was rubbed on the core's surface to avoid shear stress transition to the restraining system. The numerical model was verified by the analytical solutions developed by the other researchers. Performance of BRB system under seismic loading at ambient temperature has been well documented. However, its performance in case of fire has yet to be explored. This study showed that the failure of brace may be attributed to material strength reduction and high compressive forces, both due to temperature rise. Furthermore, limiting temperatures in the linear behavior of steel casing and concrete in BRB element for both numerical and analytical simulations were about 196°C and 225°C, respectively. Finally it is concluded that the performance of BRB at elevated temperatures was the same as that seen at room temperature; that is, the steel core yields prior to the restraining system. PMID:24526915

  1. Phase distribution and microstructural changes of self-compacting cement paste at elevated temperature

    SciTech Connect

    Ye, G. . E-mail: ye.guang@citg.tudelft.nl; Liu, X.; De Schutter, G.; Taerwe, L.; Vandevelde, P.

    2007-06-15

    Self-compacting concrete, as a new smart building material with various advanced properties, has been used for a wide range of structures and infrastructures. However little investigation have been reported on the properties of Self-compacting when it is exposed to elevated temperatures. Previous experiments on fire test have shown the differences between high performance concrete and traditional concrete at elevated temperature. This difference is largely depending on the microstructural properties of concrete matrix, i.e. the cement paste, especially on the porosity, pore size distribution and the connectivity of pores in cement pastes. In this contribution, the investigations are focused on the cement paste. The phase distribution and microstructural changes of self-compacting cement paste at elevated temperatures are examined by mercury intrusion porosimetry and scanning electron microscopy. The chemical decomposition of self-compacting cement paste at different temperatures is determined by thermogravimetric analysis. The experimental results of self-compacting cement paste are compared with those of high performance cement paste and traditional cement paste. It was found that self-compacting cement paste shows a higher change of the total porosity in comparison with high performance cement paste. When the temperature is higher than 700 deg. C, a dramatic loss of mass was observed in the self-compacting cement paste samples with addition of limestone filler. This implies that the SCC made by this type of self-compacting cement paste will probably show larger damage once exposed to fire. Investigation has shown that 0.5 kg/m{sup 3} of Polypropylene fibers in the self-compacting cement paste can avoid the damage efficiently.

  2. The effect of HVOF sprayed coatings on the elevated temperature high cycle fatigue behavior of a martensitic stainless steel

    SciTech Connect

    Tipton, A.A.

    1995-12-31

    This study reports the influence of three High Velocity Oxy-Fuel (HVOF) applied coatings on the high cycle fatigue resistance of a martensitic stainless steel substrate at room and elevated temperatures. It was found that chromium carbide and tungsten carbide coated specimens exhibited significantly lower fatigue capability compared to the substrate material at elevated temperatures while IN625 coated specimens exhibited a small beneficial effect. An attempt is made to explain the observed behavior in terms of elastic modulus mismatch, thermal expansion mismatch, residual stress and coating/substrate properties. It is concluded that coated metallic components must be analyzed as composite structures and that data generated for design properties must be performed on specimens which represent the geometry and characteristics of intended component.

  3. Elevated temperature effects on fatigue and fracture

    SciTech Connect

    Piascik, R.S.; Gangloff, R.P.; Saxena, A.

    1997-12-31

    The intent of this meeting was to reinforce the recent merger of ASTM Committees E09 on Fatigue and E24 on Fracture Mechanics, forming Committee E08 on Fatigue and Fracture. This special technical publication highlights a topical subset of the meeting, that is, research on the critical effect of temperature on the fatigue and fracture of structural materials. Papers highlighted: Integration of damage evolution, from the distributed form to that focused at a crack tip; High-resolution experimental probes of fatigue and fracture processes; Measurement and modeling of the important role of time in microstructural degradation, damage evolution, and crack growth; Models that provide quantitative predictions and are tested by high-quality experimentation; and Performance of next-generation structural metals and composites, characterized within a framework useful in component life prediction. Papers have been processed separately for inclusion on the data base.

  4. Strengths of serpentinite gouges at elevated temperatures

    USGS Publications Warehouse

    Moore, Diane E.; Lockner, D.A.; Ma, S.; Summers, R.; Byerlee, J.D.

    1997-01-01

    Serpentinite has been proposed as a cause of both low strength and aseismic creep of fault zones. To test these hypotheses, we have measured the strength of chrysotile-, lizardite-, and antigorite-rich serpentinite gouges under hydrothermal conditions, with emphasis on chrysotile, which has thus far received little attention. At 25??C, the coefficient of friction, ??, of chrysotile gouge is roughly 0.2, whereas the lizardite- and antigorite-rich gouges are at least twice as strong. The very low room temperature strength of chrysotile is a consequence of its unusually high adsorbed water content. When the adsorbed water is removed, chrysotile is as strong as pure antigorite gouge at room temperature. Heating to ???200??C causes the frictional strengths of all three gouges to increase. Limited data suggest that different polytypes of a given serpentine mineral have similar strengths; thus deformation-induced changes in polytype should not affect fault strength. At 25??C, the chrysotile gouge has a transition from velocity strengthening at low velocities to velocity weakening at high velocities, consistent with previous studies. At temperatures up to ???200??C, however, chrysotile strength is essentially independent of velocity at low velocities. Overall, chrysotile has a restricted range of velocity-strengthening behavior that migrates to higher velocities with increasing temperature. Less information on velocity dependence is available for the lizardite and antigorite gouges, but their behavior is consistent with that outlined for chrysotile. The marked changes in velocity dependence and strength of chrysotile with heating underscore the hazards of using room temperature data to predict fault behavior at depth. The velocity behavior at elevated temperatures does not rule out serpentinite as a cause of aseismic slip, but in the presence of a hydrostatic fluid pressure gradient, all varieties of serpentine are too strong to explain the apparent weakness of faults such

  5. Process Simulation of Aluminium Sheet Metal Deep Drawing at Elevated Temperatures

    SciTech Connect

    Winklhofer, Johannes; Trattnig, Gernot; Sommitsch, Christof

    2010-06-15

    Lightweight design is essential for an economic and environmentally friendly vehicle. Aluminium sheet metal is well known for its ability to improve the strength to weight ratio of lightweight structures. One disadvantage of aluminium is that it is less formable than steel. Therefore complex part geometries can only be realized by expensive multi-step production processes. One method for overcoming this disadvantage is deep drawing at elevated temperatures. In this way the formability of aluminium sheet metal can be improved significantly, and the number of necessary production steps can thereby be reduced. This paper introduces deep drawing of aluminium sheet metal at elevated temperatures, a corresponding simulation method, a characteristic process and its optimization. The temperature and strain rate dependent material properties of a 5xxx series alloy and their modelling are discussed. A three dimensional thermomechanically coupled finite element deep drawing simulation model and its validation are presented. Based on the validated simulation model an optimised process strategy regarding formability, time and cost is introduced.

  6. The mechanical behavior of extruded powder aluminum subjected to biaxial loadings at elevated temperature

    SciTech Connect

    Woods, T.O.; Berghaus, D.G.; Peacock, H.B.

    1990-12-31

    The goal of this investigation is to develop a description of the biaxial behavior of extruded powder aluminum at elevated temperature. Specimens made of extruded 101 ALCOA (Aluminum Company of America) powder aluminum and specimens made from 1100 commercial aluminum rod are tested biaxially in tension-torsion and compression-torsion loadings at the extrusion temperature. The powder aluminum is examined microscopically and stereological methods are used to give a quantified description of the material behavior in terms of changes in the laminar powder material structure. A model for the biaxial (tension-torsion) behavior of extruded powder aluminum is developed. This description is consistent with a previous analysis of behavior in pure tension.

  7. The mechanical behavior of extruded powder aluminum subjected to biaxial loadings at elevated temperature

    SciTech Connect

    Woods, T.O.; Berghaus, D.G. ); Peacock, H.B. )

    1990-01-01

    The goal of this investigation is to develop a description of the biaxial behavior of extruded powder aluminum at elevated temperature. Specimens made of extruded 101 ALCOA (Aluminum Company of America) powder aluminum and specimens made from 1100 commercial aluminum rod are tested biaxially in tension-torsion and compression-torsion loadings at the extrusion temperature. The powder aluminum is examined microscopically and stereological methods are used to give a quantified description of the material behavior in terms of changes in the laminar powder material structure. A model for the biaxial (tension-torsion) behavior of extruded powder aluminum is developed. This description is consistent with a previous analysis of behavior in pure tension.

  8. Powder processing of NiAl for elevated temperature strength

    SciTech Connect

    Whittenberger, J.D.; Hebsur, M.; Grahle, P.; Arzt, E.; Behr, R.; Zoeltzer, K.

    1997-12-31

    In an effort to superimpose two different elevated temperature strengthening mechanisms in NiAl, one lot of an oxide dispersion strengthened (ODS) NiAl powder has been milled in liquid nitrogen (cryomilled) to introduce AlN particles at the grain boundaries, and a second lot of ODS powder was simply roasted in gaseous nitrogen as an alternative means to produce AlN reinforced grain boundaries. Powder from both of these lots as well as the starting material have been consolidated by hot extrusion and tested at 1,300 K. Both nitrogen roasting and cryomilling produced AlN within the ODS NiAl matrix which strengthened the alloy; however, based on the AlN content, cryomilling is more effective.

  9. Literature survey on oxidations and fatigue lives at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Liu, H. W.; Oshida, Y.

    1984-01-01

    Nickel-base superalloys are the most complex and the most widely used for high temperature applications such as aircraft engine components. The desirable properties of nickel-base superalloys at high temperatures are tensile strength, thermomechanical fatigue resistance, low thermal expansion, as well as oxidation resistance. At elevated temperature, fatigue cracks are often initiated by grain boundary oxidation, and fatigue cracks often propagate along grain boundaries, where the oxidation rate is higher. Oxidation takes place at the interface between metal and gas. Properties of the metal substrate, the gaseous environment, as well as the oxides formed all interact to make the oxidation behavior of nickel-base superalloys extremely complicated. The important topics include general oxidation, selective oxidation, internal oxidation, grain boundary oxidation, multilayer oxide structure, accelerated oxidation under stress, stress-generation during oxidation, composition and substrate microstructural changes due to prolonged oxidation, fatigue crack initiation at oxidized grain boundaries and the oxidation accelerated fatigue crack propagation along grain boundaries.

  10. Helium and deuterium implantation in tungsten at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Cipiti, B. B.; Kulcinski, G. L.

    2005-12-01

    High temperature helium and deuterium implantation on tungsten has been studied using the University of Wisconsin inertial electrostatic confinement device. Helium or deuterium ions from a plasma source were driven into polished tungsten powder metallurgy samples. Deuterium implantation did not damage the surface of the specimens at elevated temperatures (˜1200 °C). Helium implantation resulted in a porous surface structure above 700 °C. A helium fluence scan, ion energy scan, and temperature scan were all completed. With 30 keV ions, the pore formation started just below 4 × 10 16 He +/cm 2. The pore size increased and the pore density decreased with increasing fluence and temperature. The energy scan from 20 to 80 keV showed no consistent trend.

  11. Elevated temperature mechanical properties of line pipe steels

    NASA Astrophysics Data System (ADS)

    Jacobs, Taylor Roth

    The effects of test temperature on the tensile properties of four line pipe steels were evaluated. The four materials include a ferrite-pearlite line pipe steel with a yield strength specification of 359 MPa (52 ksi) and three 485 MPa (70 ksi) yield strength acicular ferrite line pipe steels. Deformation behavior, ductility, strength, strain hardening rate, strain rate sensitivity, and fracture behavior were characterized at room temperature and in the temperature range of 200--350 °C, the potential operating range for steels used in oil production by the steam assisted gravity drainage process. Elevated temperature tensile testing was conducted on commercially produced as-received plates at engineering strain rates of 1.67 x 10 -4, 8.33 x 10-4, and 1.67 x 10-3 s-1. The acicular ferrite (X70) line pipe steels were also tested at elevated temperatures after aging at 200, 275, and 350 °C for 100 h under a tensile load of 419 MPa. The presence of serrated yielding depended on temperature and strain rate, and the upper bound of the temperature range where serrated yielding was observed was independent of microstructure between the ferrite-pearlite (X52) steel and the X70 steels. Serrated yielding was observed at intermediate temperatures and continuous plastic deformation was observed at room temperature and high temperatures. All steels exhibited a minimum in ductility as a function of temperature at testing conditions where serrated yielding was observed. At the higher temperatures (>275 °C) the X52 steel exhibited an increase in ductility with an increase in temperature and the X70 steels exhibited a maximum in ductility as a function of temperature. All steels exhibited a maximum in flow strength and average strain hardening rate as a function of temperature. The X52 steel exhibited maxima in flow strength and average strain hardening rate at lower temperatures than observed for the X70 steels. For all steels, the temperature where the maximum in both flow

  12. A model for the biaxial post-yield behavior of extruded powder aluminum at elevated temperature

    SciTech Connect

    Woods, T.O.; Berghaus, D.G. ); Peacock, H.B. )

    1990-01-01

    A model has been developed which describes the post-yield behavior of extruded powder aluminum tested biaxially in tension and torsion at elevated temperature. Plots of shear stress versus shear strain for the powder aluminum loaded in simple torsion show that the shear stress increases linearly to the yield point, then remains relatively constant in a pure plastic type of behavior. For the tension-torsion tests, there is an initial linear region up to the yield point followed by a fairly linear decrease in shear stress. A similar linear decrease in axial stress with increasing axial strain is observed in uniaxial tension tests. The model for post-yield behavior of extruded powder aluminum gives a quantified description of the macroscopic material behavior in terms of changes in the laminar powder aluminum structure.

  13. A model for the biaxial post-yield behavior of extruded powder aluminum at elevated temperature

    SciTech Connect

    Woods, T.O.; Berghaus, D.G.; Peacock, H.B.

    1990-12-31

    A model has been developed which describes the post-yield behavior of extruded powder aluminum tested biaxially in tension and torsion at elevated temperature. Plots of shear stress versus shear strain for the powder aluminum loaded in simple torsion show that the shear stress increases linearly to the yield point, then remains relatively constant in a pure plastic type of behavior. For the tension-torsion tests, there is an initial linear region up to the yield point followed by a fairly linear decrease in shear stress. A similar linear decrease in axial stress with increasing axial strain is observed in uniaxial tension tests. The model for post-yield behavior of extruded powder aluminum gives a quantified description of the macroscopic material behavior in terms of changes in the laminar powder aluminum structure.

  14. Structural materials for space applications

    NASA Technical Reports Server (NTRS)

    Tenney, Darrel R.

    1989-01-01

    The long-term performance of structural materials in the space environment is a key research activity within NASA. The primary concerns for materials in low Earth orbit (LEO) are atomic oxygen erosion and space debris impact. Atomic oxygen studies have included both laboratory exposures in atomic oxygen facilities and flight exposures using the Shuttle. Characterization of atomic oxygen interaction with materials has included surface recession rates, residual mechanical properties, optical property measurements, and surface analyses to establish chemical changes. The Long Duration Exposure Facility (LDEF) is scheduled to be retrieved in 1989 and is expected to provide a wealth of data on atomic oxygen erosion in space. Hypervelocity impact studies have been conducted to establish damage mechanisms and changes in mechanical properties. Samples from LDEF will be analyzed to determine the severity of space debris impact on coatings, films, and composites. Spacecraft placed in geosynchronous Earth orbit (GEO) will be subjected to high doses of ionizing radiation which for long term exposures will exceed the damage threshold of many polymeric materials. Radiation interaction with polymers can result in chain scission and/or cross-linking. The formation of low molecular weight products in the epoxy plasticize the matrix at elevated temperatures and embrittle the matrix at low temperatures. This affects both the matrix-dominated mechanical properties and the dimensional stability of the composite. Embrittlement of the matrix at low temperatures results in enhanced matrix microcracking during thermal cycling. Matrix microcracking changes the coefficient of thermal expansion (CTE) of composite laminates and produces permanent length changes. Residual stress calculations were performed to estimate the conditions necessary for microcrack development in unirradiated and irradiated composites. The effects of UV and electron exposure on the optical properties of transparent

  15. Elevated temperature deformation of TD-nickel base alloys

    NASA Technical Reports Server (NTRS)

    Petrovic, J. J.; Kane, R. D.; Ebert, L. J.

    1972-01-01

    Sensitivity of the elevated temperature deformation of TD-nickel to grain size and shape was examined in both tension and creep. Elevated temperature strength increased with increasing grain diameter and increasing L/D ratio. Measured activation enthalpies in tension and creep were not the same. In tension, the internal stress was not proportional to the shear modulus. Creep activation enthalpies increased with increasing L/D ratio and increasing grain diameter, to high values compared with that of the self diffusion enthalpy. It has been postulated that two concurrent processes contribute to the elevated temperature deformation of polycrystalline TD-nickel: (1) diffusion controlled grain boundary sliding, and (2) dislocation motion.

  16. Tantalum alloys resist creep deformation at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Buckman, R. W., Jr.

    1966-01-01

    Dispersion-strengthened tantalum-base alloys possess high strength and good resistance to creep deformation at elevated temperatures in high vacuum environments. They also have ease of fabrication, good weldability, and corrosion resistance to molten alkali metals.

  17. Integrated research in constitutive modelling at elevated temperatures, part 1

    NASA Technical Reports Server (NTRS)

    Haisler, W. E.; Allen, D. H.

    1986-01-01

    Topics covered include: numerical integration techniques; thermodynamics and internal state variables; experimental lab development; comparison of models at room temperature; comparison of models at elevated temperature; and integrated software development.

  18. Plastic Deformation Characteristics Of AZ31 Magnesium Alloy Sheets At Elevated Temperature

    NASA Astrophysics Data System (ADS)

    Park, Jingee; Lee, Jongshin; You, Bongsun; Choi, Seogou; Kim, Youngsuk

    2007-05-01

    Using lightweight materials is the emerging need in order to reduce the vehicle's energy consumption and pollutant emissions. Being a lightweight material, magnesium alloys are increasingly employed in the fabrication of automotive and electronic parts. Presently, magnesium alloys used in automotive and electronic parts are mainly processed by die casting. The die casting technology allows the manufacturing of parts with complex geometry. However, the mechanical properties of these parts often do not meet the requirements concerning the mechanical properties (e.g. endurance strength and ductility). A promising alternative can be forming process. The parts manufactured by forming could have fine-grained structure without porosity and improved mechanical properties such as endurance strength and ductility. Because magnesium alloy has low formability resulted form its small slip system at room temperature it is usually formed at elevated temperature. Due to a rapid increase of usage of magnesium sheets in automotive and electronic industry it is necessary to assure database for sheet metal formability and plastic yielding properties in order to optimize its usage. Especially, plastic yielding criterion is a critical property to predict plastic deformation of sheet metal parts in optimizing process using CAE simulation. Von-Mises yield criterion generally well predicts plastic deformation of steel sheets and Hill'1979 yield criterion predicts plastic deformation of aluminum sheets. In this study, using biaxial tensile test machine yield loci of AZ31 magnesium alloy sheet were obtained at elevated temperature. The yield loci ensured experimentally were compared with the theoretical predictions based on the Von-Mises, Hill, Logan-Hosford, and Barlat model.

  19. Reduced graphene oxides: light-weight and high-efficiency electromagnetic interference shielding at elevated temperatures.

    PubMed

    Wen, Bo; Cao, Maosheng; Lu, Mingming; Cao, Wenqiang; Shi, Honglong; Liu, Jia; Wang, Xixi; Jin, Haibo; Fang, Xiaoyong; Wang, Wenzhong; Yuan, Jie

    2014-06-01

    Chemical graphitized r-GOs, as the thinnest and lightest material in the carbon family, exhibit high-efficiency electromagnetic interference (EMI) shielding at elevated temperature, attributed to the cooperation of dipole polarization and hopping conductivity. The r-GO composites show different temperature-dependent imaginary permittivities and EMI shielding performances with changing mass ratio. PMID:24648151

  20. Electromigration in Sintered Nanoscale Silver Films at Elevated Temperature

    NASA Astrophysics Data System (ADS)

    Calata, Jesus N.; Lu, Guo-Quan; Ngo, Khai; Nguyen, Luu

    2014-01-01

    Sintered nanoscale silver is a promising interconnection material for semiconductor devices because it provides improved joint properties compared with solder and wire bonds. It has higher electrical and thermal conductivity and is capable of higher operating temperature. Joints with die shear strength above 20 MPa can be formed at around 250°C even without applied pressure. Sintered silver joints were also found to be an order of magnitude more reliable than solder joints and wire bonds. In this work, the electromigration behavior of sintered nanosilver material under conditions of high applied current density and elevated temperature was investigated. Thin strips of sintered nanosilver formed on ceramic substrates were tested under current densities exceeding 150 kA/cm2 at temperatures of 150°C and above. Results based on the percentage change in sample resistance showed that the sintered silver lasted at least ten times longer than aluminum wire bonds. Examination of failed strips revealed that hairline cracks formed during sintering were the main cause of failure. Otherwise, defect-free samples exhibited a 10-fold increase in lifetime over wire bonds under similar conditions.

  1. Mechanisms of time-dependent crack growth at elevated temperature

    SciTech Connect

    Saxena, A.; Stock, S.R.

    1990-04-15

    Objective of this 3-y study was to conduct creep and creep-fatigue crack growth experiments and to characterize the crack tip damage mechanisms in a model material (Cu-1wt%Sb), which is known to cavitate at grain boundaries under creep deformation. Results were: In presence of large scale cavitation damage and crack branching, time rate of creep crack growth da/dt does not correlate with C[sub t] or C[sup *]. When cavitation damage is constrained, da/dt is characterized by C[sub t]. Area fraction of grain boundary cavitated is the single damage parameter for the extent of cavitation damage ahead of crack tips. C[sub t] is used for the creep-fatigue crack growth behavior. In materials prone to rapid cavity nucleation, creep cracks grow faster initially and then reach a steady state whose growth rate is determined by C[sub t]. Percent creep life exhausted correlates with average cavity diameter and fraction of grain boundary area occupied by cavities. Synchrotron x-ray tomographic microscopy was used to image individual cavities in Cu-1wt% Sb. A methodology was developed for predicting the remaining life of elevated temperature power plant components; (C[sub t])[sub avg] was used to correlate creep-fatigue crack growth in Cr-Mo and Cr-Mo-V steel and weldments.

  2. Structural materials and components

    NASA Technical Reports Server (NTRS)

    Gagliani, John (Inventor); Lee, Raymond (Inventor)

    1982-01-01

    High density structural (blocking) materials composed of a polyimide filled with glass microballoons and methods for making such materials. Structural components such as panels which have integral edgings and/or other parts made of the high density materials.

  3. Elevated Temperature, Notched Compression Performance of Out of Autoclave Processed Composites

    NASA Technical Reports Server (NTRS)

    Grimsley, Brian W.; Sutter, James K.; Dixon, Genevieve D.; Smeltzer, Satn S.

    2013-01-01

    Curved honeycomb sandwich panels composed of carbon fiber reinforced toughened-epoxy polymer facesheets are being evaluated for potential use as payload fairing components on the NASA heavy-lift space launch system (HL-SLS). These proposed composite sandwich panels provide the most efficient aerospace launch structures, and offer mass and thermal advantages when compared with existing metallic payload fairing structures. NASA and industry are investigating recently developed carbon fiber epoxy prepreg systems which can be fabricated using out-of autoclave (OOA) processes. Specifically, OOA processes using vacuum pressure in an oven and thereby significantly reducing the cost associated with manufacturing large (up to 10 m diameter) composite structures when compared with autoclave. One of these OOA composite material systems, CYCOM(R) 5320-1, was selected for manufacture of a 1/16th scale barrel portion of the payload fairing; such that, the system could be compared with the well-characterized prepreg system, CYCOM(R) 977-3, typically processed in an autoclave. Notched compression coupons for each material were obtained from the minimum-gauge flat laminate [60/-60/0]S witness panels produced in this manufacturing study. The coupons were also conditioned to an effective moisture equilibrium point and tested according to ASTM D6484M-09 at temperatures ranging from 25 C up to 177 C. The results of this elevated temperature mechanical characterization study demonstrate that, for thin coupons, the OHC strength of the OOA laminate was equivalent to the flight certified autoclave processed composite laminates; the limitations on the elevated temperature range are hot-wet conditions up to 163 C and are only within the margins of testing error. At 25 C, both the wet and dry OOA material coupons demonstrated greater OHC failure strengths than the autoclave processed material laminates. These results indicate a substantial improvement in OOA material development and

  4. Elevated temperature fiber push-out testing

    SciTech Connect

    Eldridge, J.I.

    1995-10-01

    The potential use of fiber-reinforced composite materials for high temperature applications makes the development of interface test methodology at those high temperatures very desirable. A facility for performing high temperature fiber push-out tests will be described with emphasis on critical issues in experimental procedure. Examples from several composite systems illustrate the temperature dependence and environmental sensitivity of fiber debonding and sliding. Interpretation of the temperature dependence will be made primarily in terms of changes in residual stresses along with additional effects due to changes in matrix ductility and interfacial wear. Examples will show that high temperature fiber push-out testing can often distinguish between chemical and frictional fiber/matrix bonding in cases where room temperature only testing cannot.

  5. Elevated temperature crack growth in advanced powder metallurgy aluminum alloys

    NASA Technical Reports Server (NTRS)

    Porr, William C., Jr.; Gangloff, Richard P.

    1990-01-01

    Rapidly solidified Al-Fe-V-Si powder metallurgy alloy FVS0812 is among the most promising of the elevated temperature aluminum alloys developed in recent years. The ultra fine grain size and high volume fraction of thermally stable dispersoids enable the alloy to maintain tensile properties at elevated temperatures. In contrast, this alloy displays complex and potentially deleterious damage tolerant and time dependent fracture behavior that varies with temperature. J-Integral fracture mechanics were used to determine fracture toughness (K sub IC) and crack growth resistance (tearing modulus, T) of extruded FVS0812 as a function of temperature. The alloy exhibits high fracture properties at room temperature when tested in the LT orientation, due to extensive delamination of prior ribbon particle boundaries perpendicular to the crack front. Delamination results in a loss of through thickness constraint along the crack front, raising the critical stress intensity necessary for precrack initiation. The fracture toughness and tensile ductility of this alloy decrease with increasing temperature, with minima observed at 200 C. This behavior results from minima in the intrinsic toughness of the material, due to dynamic strain aging, and in the extent of prior particle boundary delaminations. At 200 C FVS0812 fails at K levels that are insufficient to cause through thickness delamination. As temperature increases beyond the minimum, strain aging is reduced and delamination returns. For the TL orientation, K (sub IC) decreased and T increased slightly with increasing temperature from 25 to 316 C. Fracture in the TL orientation is governed by prior particle boundary toughness; increased strain localization at these boundaries may result in lower toughness with increasing temperature. Preliminary results demonstrate a complex effect of loading rate on K (sub IC) and T at 175 C, and indicate that the combined effects of time dependent deformation, environment, and strain aging

  6. Palladium based cermet composite for hydrogen separation at elevated temperature

    NASA Astrophysics Data System (ADS)

    Tsai, Yen-Chang; Lin, Chien-Cheng; Lin, Wei-Lin; Wang, Jeng-Han; Chen, San-Yuan; Lin, Pang; Wu, Pu-Wei

    2015-01-01

    A cermet composite consisting of palladium and BaCe0.4Zr0.4Gd0.1Dy0.1O3-x (BCZGD) is fabricated by mixing palladium and BCZGD powders in a ball mill, followed by pressing and sintering at 1450 °C for 24 h in air. The Pd-BCZGD cermet demonstrates impressive hydrogen permeation flux in a mixture of hydrogen and carbon dioxide at elevated temperature, in which the palladium plays the predominant role of facile transport in the hydrogen atoms whereas the BCZGD provides channels for proton conduction. Material characterization including scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermo-gravimetric analysis (TGA) are performed. XRD patterns indicate pure phases of fcc palladium and perovskite BCZGD. SEM images and element mapping suggest a homogeneous mixture of cermet without noticeable defect and phase segregation. TGA results confirm stability of the cermet against carbon dioxide without chemical decomposition. The hydrogen permeation flux is determined via a gas chromatography from 400 to 700 °C at various hydrogen concentration gradients. We record a hydrogen flux of 1.25 cm3 min-1 cm-2 in 50% hydrogen and 50% carbon dioxide at 700 °C, with a selectivity of H2/CO2 approaching infinity.

  7. Mesoscale Molecular Dynamics of Geomaterials: the Glass Transition, Long-Range Structure of Amorphous Silicates and Relation between Structure, Dynamics and Properties of geomaterials at elevated Temperature and Pressure

    SciTech Connect

    Frank Spera

    2006-07-31

    Objectives: Our aims were (1) Large particle-number Molecular Dynamics (MD) simulations of molten silicate and aluminosilicate geomaterials (e.g., CaAl{sub 2}Si{sub 2}O{sub 8}, MgSiO{sub 3}, Mg{sub 2}SiO{sub 4}) with emphasis on understanding the connection between atomic structure and properties at temperatures and pressures characteristic of Earth's mantle (2) Study of the transport properties and equations of state for silicate liquids based on the MD results (3) Development of geochemical models for the evolution of crustal magma bodies undergoing simultaneous assimilation, fractional crystallization, periodic recharge and periodic eruption and application to magmatic systems (4) Study of current-day rates of generation and eruption of magma on earth.

  8. Novel silica surface charge density mediated control of the optical properties of embedded optically active materials and its application for fiber optic pH sensing at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Wang, Congjun; Ohodnicki, Paul R.; Su, Xin; Keller, Murphy; Brown, Thomas D.; Baltrus, John P.

    2015-01-01

    Silica and silica incorporated nanocomposite materials have been extensively studied for a wide range of applications. Here we demonstrate an intriguing optical effect of silica that, depending on the solution pH, amplifies or attenuates the optical absorption of a variety of embedded optically active materials with very distinct properties, such as plasmonic Au nanoparticles, non-plasmonic Pt nanoparticles, and the organic dye rhodamine B (not a pH indicator), coated on an optical fiber. Interestingly, the observed optical response to varying pH appears to follow the surface charge density of the silica matrix for all the three different optically active materials. To the best of our knowledge, this optical effect has not been previously reported and it appears universal in that it is likely that any optically active material can be incorporated into the silica matrix to respond to solution pH or surface charge density variations. A direct application of this effect is for optical pH sensing which has very attractive features that can enable minimally invasive, remote, real time and continuous distributed pH monitoring. Particularly, as demonstrated here, using highly stable metal nanoparticles embedded in an inorganic silica matrix can significantly improve the capability of pH sensing in extremely harsh environments which is of increasing importance for applications in unconventional oil and gas resource recovery, carbon sequestration, water quality monitoring, etc. Our approach opens a pathway towards possible future development of robust optical pH sensors for the most demanding environmental conditions. The newly discovered optical effect of silica also offers the potential for control of the optical properties of optically active materials for a range of other potential applications such as electrochromic devices.Silica and silica incorporated nanocomposite materials have been extensively studied for a wide range of applications. Here we demonstrate an

  9. Materials and structures

    NASA Technical Reports Server (NTRS)

    Venneri, Samuel L.

    1988-01-01

    Information on materials and structures for use in space is given in viewgraph form. Information is given on the Materials and Structures Division of NASA's Office of Aeronautics and Space Technology. The Division's space research and development budget is given. Further information is given on space materials and structures, space environmental effects, radiation effects, high temperature materials research, metal matrix composites, SiC fiber reinforced titanium alloys, structural dynamics, and control of flexible structures.

  10. Novel silica surface charge density mediated control of the optical properties of embedded optically active materials and its application for fiber optic pH sensing at elevated temperatures.

    PubMed

    Wang, Congjun; Ohodnicki, Paul R; Su, Xin; Keller, Murphy; Brown, Thomas D; Baltrus, John P

    2015-02-14

    Silica and silica incorporated nanocomposite materials have been extensively studied for a wide range of applications. Here we demonstrate an intriguing optical effect of silica that, depending on the solution pH, amplifies or attenuates the optical absorption of a variety of embedded optically active materials with very distinct properties, such as plasmonic Au nanoparticles, non-plasmonic Pt nanoparticles, and the organic dye rhodamine B (not a pH indicator), coated on an optical fiber. Interestingly, the observed optical response to varying pH appears to follow the surface charge density of the silica matrix for all the three different optically active materials. To the best of our knowledge, this optical effect has not been previously reported and it appears universal in that it is likely that any optically active material can be incorporated into the silica matrix to respond to solution pH or surface charge density variations. A direct application of this effect is for optical pH sensing which has very attractive features that can enable minimally invasive, remote, real time and continuous distributed pH monitoring. Particularly, as demonstrated here, using highly stable metal nanoparticles embedded in an inorganic silica matrix can significantly improve the capability of pH sensing in extremely harsh environments which is of increasing importance for applications in unconventional oil and gas resource recovery, carbon sequestration, water quality monitoring, etc. Our approach opens a pathway towards possible future development of robust optical pH sensors for the most demanding environmental conditions. The newly discovered optical effect of silica also offers the potential for control of the optical properties of optically active materials for a range of other potential applications such as electrochromic devices. PMID:25572664

  11. Gas Generation Testing of Neptunium Oxide at Elevated Temperature

    SciTech Connect

    Duffey, JM

    2004-01-30

    Elevated temperature gas generation tests have been conducted using neptunium dioxide produced on a laboratory scale using the HB-Line Phase II flowsheet. These tests were performed to determine what effect elevated temperatures would have on the neptunium dioxide in comparison to neptunium dioxide tested at ambient temperature. The headspace gas compositions following storage at elevated temperatures associated with normal conditions of transport (NCT) have been measured. These test results show an increase in hydrogen generation rate at elevated temperature and significant removal of oxygen from the headspace gas. The elevated temperature gas generation tests described in this report involved heating small test vessels containing neptunium dioxide and measuring the headspace gas pressure and composition at the end of the test period. Four samples were used in these tests to evaluate the impact of process variables on the gas generation rate. Two samples were calcined to 600 degrees Celsius and two were calcined to 650 degrees Celsius. Each test vessel contained approximately 9.5 g of neptunium dioxide. Following exposure to 75 per cent relative humidity (RH) for five days, these samples were loaded in air and then heated to between 105 and 115 degrees Celsius for about one month. At the conclusion of the test period, the headspace gas of each container was analyzed using a micro-gas chromatograph installed in the glovebox where the experiments were conducted. The pressure, volume, and composition data for the headspace gas samples were used to calculate average H2 generation rates.

  12. Failure mechanisms of notched laminated composites under compressive loading at room and elevated temperature

    NASA Astrophysics Data System (ADS)

    Ahn, Jung Hyun

    1999-10-01

    Understanding the mechanisms of failure of composite structures and developing mechanism based failure criteria are important considerations in designing structures made of composite materials. The compressive response of composite materials and structures has received considerable attention due to their significance in the aerospace industry and the complexity associated with compressive failure. Several competing failure mechanisms such as fiber instability, fiber/matrix interfacial failure, fiber microbuckling/kinking, delamination initiation and delamination buckling may become active in compressive loading. Environmental effect such as an elevated temperature can alter and affect these failure mechanisms. In this thesis, a micromechanics based finite element predictive model for notched strength of multidirectional laminates is presented. The in-situ shear response of the matrix, the fiber mechanical properties, the lay-up (stacking sequence) and fiber volume fraction serve as input to the model. The prediction of the model is found to match favorably with experimental data. The effect of ply angle and its influence on the failure mechanism are quantified and compared with a set of available experimental data. The present work is the first development of a non-empirical mechanics based failure prediction methodology for notched compressive strength of composite laminates. Both an experimental and an analytical study are presented herein.

  13. Structural materials and components

    NASA Technical Reports Server (NTRS)

    Gagliani, John (Inventor); Lee, Raymond (Inventor)

    1982-01-01

    High density structural (blocking) materials composed of a polyimide filled with glass microballoons. Structural components such as panels which have integral edgings and/or other parts made of the high density materials.

  14. Structural materials and components

    NASA Technical Reports Server (NTRS)

    Gagliani, John (Inventor); Lee, Raymond (Inventor)

    1983-01-01

    High density structural (blocking) materials composed of a polyimide filled with glass microballoons. Structural components such as panels which have integral edgings and/or other parts made of the high density materials.

  15. Lightweight Materials & Structures

    NASA Video Gallery

    The Lightweight Materials and Structures (LMS) project will mature high-payoff structures and materials technologies that have direct application to NASA’s future space exploration needs.One of the...

  16. Elevated Temperature Compressive Properties of Zr-Modified Nial

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Noebe, R. D.

    1996-01-01

    Small Zr additions are known to substantially affect the deformation behavior and strength of polycrystalline NiAl, yet little information is currently available regarding the high-temperature properties of such alloys. Utilizing prealloyed powder technology, a series of four NiAl alloys have been produced containing from 0.05 to 0.7 at. pct Zr. The creep behavior of these alloys was characterized in compression between 1000 and 1400 K at strain rates ranging from approx. O.1 to 10(exp -9)/ sec. All the Zr-modified alloys were significantly stronger than binary NiAl under lower temperature and faster strain-rate conditions; however, the single-phase materials (Zr less than or equal to 0.1 at. pct) and binary NiAl had similar strengths at high temperatures and slow strain rates. The two-phase NiAl-Ni, AlZr alloys containing 0.3 and 0.7 at. pct Zr had nearly identical strengths. While the two-phase alloys were stronger than the single-phase materials at all test conditions, the degree of microstructural damage in the two-phase alloys due to internal oxidation during testing appeared to increase with Zr level. Balancing the poor oxidation behavior with the consistent strength advantage of the two-phase alloys, it is concluded that optimum elevated-temperature properties could be obtained in Heusler-strengthened NiAl containing between 0.1 and 0.3 at. pct Zr.

  17. An x-ray absorption spectroscopy study of Mo oxidation in Pb at elevated temperatures

    SciTech Connect

    Liu, Shanshan; Olive, Daniel; Terry, Jeff; Segre, Carlo U.

    2009-06-30

    The corrosion of fuel cladding and structural materials by lead and lead-bismuth eutectic in the liquid state at elevated temperatures is an issue that must be considered when designing advanced nuclear systems and high-power spallation neutron targets. In this work, lead corrosion studies of molybdenum were performed to investigate the interaction layer as a function of temperature by X-ray absorption spectroscopy. In situ X-ray absorption measurements on a Mo substrate with a 3-6 {micro}m layer of Pb deposited by thermal evaporation were performed at temperatures up to 900 C and at a 15{sup o} angle to the incident X-rays. The changes in the local atomic structure of the corrosion layer are visible in the difference extended X-ray absorption fine structure and the linear combination fitting of the X-ray absorption near-edge structure to as-deposited molybdenum sample and molybdenum oxide (MoO{sub 2} and MoO{sub 3}) standards. The data are consistent with the appearance of MoO{sub 3} in an intermediate temperature range (650-800 C) and the more stable MoO{sub 2} phase dominating at high and low temperatures.

  18. Characterization of interphase environmental degradation at elevated temperature of fiber-reinforced TMCs

    NASA Astrophysics Data System (ADS)

    Matikas, Theodore E.

    2009-03-01

    Fiber reinforced metallic composite materials are being considered for a number of applications because of their attractive mechanical properties as compared to monolithic metallic alloys. An engineered interphase, including the bond strength between the composite's constituents, contributes to a large extent to the improvement of strength and stiffness properties of this class of materials. However, in high temperature applications, where combination of cyclic loading with environmental effects is expected, consideration should be given to interphase degradation, especially in the vicinity of stress risers, such as notches and holes. The applicability of damage tolerance analysis in structural components made of titanium matrix composite materials designed to operate under high temperature environments would depend on the availability of adequate characterization methods for the evaluation of interfacial degradation. The objective of this work is to provide a basic understanding of interfacial degradation mechanisms due to oxidation in environmentally exposed titanium-based composites subjected to cyclic stresses. A nondestructive method has been developed enabling highresolution monitoring of interfacial damage initiation and accumulation as well as surface/subsurface cracking behavior during interrupted fatigue tests. This nondestructive technique is based on surface acoustic wave propagation in the composites and can detect minute changes in elastic properties of the interfacial region due to elevated temperatures as well as oxygen effects.

  19. Effect of curing conditions on the dimensional and thermal stability of calcium phosphate cement for elevated temperature applications

    SciTech Connect

    Blom, Johan; Rahier, Hubert; Wastiels, Jan

    2014-12-15

    Calcium phosphate cements (CPCs) are attractive materials for elevated temperature applications, like moulds to process thermoplastics up to 300 °C. The CPC resulting from the reaction of wollastonite with phosphoric acid cured at room temperature however contains hydrated phases like brushite, and is thus not stable when exposed to temperatures above 200 °C. A non-contact method based on digital image correlation demonstrated that isothermal curing at 60 °C reduces the thermal shrinkage up to 300 °C by 25%. This curing method results in the direct formation of the more stable monetite in a shorter curing time. The correlated results of TGA, pH of the filtration water, and DSC analysis on partially cured material indicate this. XRD diffractograms and SEM images in combination with EDX show the evolution of the transformation of wollastonite into monetite, and the structure and morphology of the formed material.

  20. Elevated temperature creep properties for selected active metal braze alloys

    SciTech Connect

    Stephens, J.J.

    1997-02-01

    Active metal braze alloys reduce the number of processes required for the joining of metal to ceramic components by eliminating the need for metallization and/or Ni plating of the ceramic surfaces. Titanium (Ti), V, and Zr are examples of active element additions which have been used successfully in such braze alloys. Since the braze alloy is expected to accommodate thermal expansion mismatch strains between the metal and ceramic materials, a knowledge of its elevated temperature mechanical properties is important. In particular, the issue of whether or not the creep strength of an active metal braze alloy is increased or decreased relative to its non-activated counterpart is important when designing new brazing processes and alloy systems. This paper presents a survey of high temperature mechanical properties for two pairs of conventional braze alloys and their active metal counterparts: (a) the conventional 72Ag-28Cu (Cusil) alloy, and the active braze alloy 62.2Ag- 36.2Cu-1.6Ti (Cusil ABA), and (b) the 82Au-18Ni (Nioro) alloy and the active braze alloy Mu-15.5M-0.75Mo-1.75V (Nioro ABA). For the case of the Cusil/Cusil ABA pair, the active metal addition contributes to solid solution strengthening of the braze alloy, resulting in a higher creep strength as compared to the non-active alloy. In the case of the Nioro/Nioro ABA pair, the Mo and V additions cause the active braze alloy to have a two-phase microstructure, which results in a reduced creep strength than the conventional braze alloy. The Garofalo sinh equation has been used to quantitatively describe the stress and temperature dependence of the deformation behavior. It will be observed that the effective stress exponent in the Garofalo sinh equation is a function of the instantaneous value of the stress argument.

  1. Materials and structures

    NASA Technical Reports Server (NTRS)

    Saito, Theodore T.; Langenbeck, Sharon L.; Al-Jamily, Ghanim; Arnold, Joe; Barbee, Troy; Coulter, Dan; Dolgin, Ben; Fichter, Buck; George, Patricia; Gorenstein, Paul

    1992-01-01

    Materials and structures technology covers a wide range of technical areas. Some of the most pertinent issues for the Astrotech 21 missions include dimensionally stable structural materials, advanced composites, dielectric coatings, optical metallic coatings for low scattered light applications, low scattered light surfaces, deployable and inflatable structures (including optical), support structures in 0-g and 1-g environments, cryogenic optics, optical blacks, contamination hardened surfaces, radiation hardened glasses and crystals, mono-metallic telescopes and instruments, and materials characterization. Some specific examples include low coefficients of thermal expansion (CTE) structures (0.01 ppm/K), lightweight thermally stable mirror materials, thermally stable optical assemblies, high reliability/accuracy (1 micron) deployable structures, and characterization of nanometer level behavior of materials/structures for interferometry concepts. Large filled-aperture concepts will require materials with CTE's of 10(exp 9) at 80 K, anti-contamination coatings, deployable and erectable structures, composite materials with CTE's less than 0.01 ppm/K and thermal hysteresis, 0.001 ppm/K. Gravitational detection systems such as LAGOS will require rigid/deployable structures, dimensionally stable components, lightweight materials with low conductivity, and high stability optics. The Materials and Structures panel addressed these issues and the relevance of the Astrotech 21 mission requirements by dividing materials and structures technology into five categories. These categories, the necessary development, and applicable mission/program development phasing are summarized. For each of these areas, technology assessments were made and development plans were defined.

  2. Hot deformation behaviour of alloys for applications at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Voyzelle, Benoit

    The present study investigated the deformation behaviour, microstructure evolution and fracture behaviour under hot working conditions of alloys designed for elevated-temperature applications. For this purpose, iron-aluminum and titanium-aluminum alloys were selected and their compositions are: Fe-8.5wt%Al-5.5Cr-2.0Mo-0.2Zr-0.03C, Fe-16.5Al-5.5Cr-1.0Nb-0.05C and Ti-33.3Al-2.8Mn-4.8Nb. These alloys were tested in the as-cast condition and in the form of hot-rolled + annealed plate for the iron-aluminum alloys and in the HIP'ed condition for the titanium-aluminum alloy. Isothermal compression tests were carried out with a Gleeble 2000 over a range of temperatures from 800 to 1250°C and constant strain rates from 10-3 to 10 s-1. In general, the flow curves are marked by a peak stress and softening which decline as temperature rises, and a flow stress which diminishes with rise in temperature and decrease in strain rate. The flow behaviour at peak stress (sigmap) and 0.5 true strain of these materials was described well by the Zener-Hollomon parameter Z=3˙exp /RTQHW , where Z=K3sinha sn . A numerical curve-fitting method was used to yield values of the following parameters: (i) stress exponent, n and (ii) activation energy, QHW . The dynamic material modeling approach was performed to extract from hot compression data: (i) the strain rate sensitivity parameter, m, (ii) the efficiency of power dissipation, eta, and (iii) the instability parameter, xi. The microstructure evolution and fracture behaviour were assessed using optical and electron microscopy. The deformation processes occuring were determined by correlation of the sigma-epsilon curves, m and microstructural observations. The resulting deformation map indicates that at lower temperatures and higher strain rates, the dominant restoration occurs by dynamic recovery, while at lower strain rates and higher temperatures dynamic recrystallization is the operative mode. At the highest temperatures, dynamic

  3. DOES CRITICAL MASS DECREASE AS TEMPERATURE INCREASES: A REVIEW OF FIVE BENCHMARK EXPERIMENTS THAT SPAN A RANGE OF ELEVATED TEMPERATURES AND CRITICAL CONFIGURATIONS

    SciTech Connect

    Yates, K.

    2009-06-10

    conditions examined, modeling of the systems at room temperature is conservative as compared to modeling the systems at elevated temperatures, it is possible to design a system in which the critical mass at room temperature is non-conservative compared to a system at elevated temperatures. As the temperature of the systems evaluated in this review was increased, the system's overall {alpha}{sub T} was negative at elevated temperatures. Furthermore, the review demonstrates that to accurate asses the effect of increased temperature on a system's k{sub eff}, changes in fissile, moderator, cladding, and, in some cases, structural material cross sections must be combined with other factors that influence reactivity, such as volumetric thermal expansion of fissile, moderating, reflector, and other interacting media. Altering the microscopic cross sections of fissile and moderating regions for temperature changes, without adjusting the corresponding densities at elevated temperatures can lead to an incorrect assessment of the impact of elevated temperature on a fissile system.

  4. Upsettability and forming limit of magnesium alloys at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Park, Heung Sik; Kim, Si Pom; Park, Young Chul; Park, Joon Hong; Baek, Seung Gul

    2012-11-01

    In recent years, Magnesium (Mg) and its alloys have become a center of special interest in the automotive industry. Due to their high specific mechanical properties, they offer a significant weight saving potential in modern vehicle constructions. Most Mg alloys show very good machinability and processability, and even the most complicated die casting parts can be easily produced. In this study, Microstructure, Vickers hardness and tensile tests were examined and performed for each specimen to verify effects of forming conditions. Also to verify upsettability and forming limit of the specimen at room temperature and elevated temperature, upsetting experiments were performed. For comparison, experiments at elevated temperature were performed for various Mg alloy, such as AZ31, AZ91, and AM50. The experimental results were compared with those of CAE analysis to propose forming limit of Magnesium alloys.

  5. Mechanical properties of polyimide coated optical fibers at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Huang, Lei; Dyer, Robert S.; Lago, Ralph J.; Stolov, Andrei A.; Li, Jie

    2016-03-01

    High temperature mechanical strength and reliability of optical fibers have become important subjects as optical fibers are increasingly used for harsher environments. Theories and models of fiber mechanical properties established for traditional telecommunications applications may need to be validated for applications at elevated temperatures. In this paper, we describe the test setup for high temperature tensile strength of fiber and report initial results of dynamic tensile strength of polyimide coated optical fiber at 300 and 350ºC for different heating time intervals. The results are compared with room temperature strength data, data available in the literature, and our earlier work on thermogravimetric analysis (TGA) weight loss of the polyimide coating and the observations on surface morphology at elevated temperatures. Interesting observations are discussed and possible explanations are proposed.

  6. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Loewy, R. G.; Wiberley, S. E.

    1985-01-01

    Various topics relating to composite structural materials for use in aircraft structures are discussed. The mechanical properties of high performance carbon fibers, carbon fiber-epoxy interface bonds, composite fractures, residual stress in high modulus and high strength carbon fibers, fatigue in composite materials, and the mechanical properties of polymeric matrix composite laminates are among the topics discussed.

  7. Modal Acoustic Emission of Damage Accumulation in Woven SiC/SiC at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Morscher, G. N.

    1998-01-01

    Ceramic matrix composites exhibit significant nonlinear stress-strain behavior that makes them attractive as potential materials for many high temperature applications. The mechanisms for this nonlinear stress-strain behavior are all associated with various types of damage in the composites, e.g. transverse matrix cracks and individual fiber failures. Modal acoustic emission has been employed to aid in discerning the damage accumulation that occurs during elevated temperature tensile stress-rupture of woven Hi-Nicalon fiber, BN interphase, SiC matrix composites. It is shown that modal acoustic emission is an effective monitor of the relative damage accumulation in the composites and locator of the damage and failure events as a function of strain (stress), time at temperature, and temperature gradients along the length of the elevated temperature test specimen.

  8. Composite coatings for elevated temperature erosion-corrosion protection in fossil-fueled boilers

    SciTech Connect

    Verstak, A.; Wang, B.; Baranovski, V.; Beliaev, A.

    1998-12-31

    Fluidized bed combustors components suffer severe erosion, frequently accomplished by corrosive gases attack at elevated temperatures. The tubes damage rate depends on the boiler design bed constituents and combustion parameters, however an accelerated metal wastage is usually found in the same specific areas of different boilers. New HVOF sprayed coatings are developed for the tube erosion-corrosion protection, based on Cr{sub 2}C{sub 2}/Ni-Cr, Cr-Ti-C/Ni-Cr-Mo, and Al{sub 2}O{sub 3}/NiAl composite materials. The combustion arc Fe-Cr-C coatings were found as an economical solution for relatively low erosion rate zones. The coatings properties and behavior under simulated elevated temperature erosion conditions and in the operating boilers are discussed.

  9. Corrosion resistant coatings suitable for elevated temperature application

    DOEpatents

    Chan, Kwai S.; Cheruvu, Narayana Sastry; Liang, Wuwei

    2012-07-31

    The present invention relates to corrosion resistance coatings suitable for elevated temperature applications, which employ compositions of iron (Fe), chromium (Cr), nickel (Ni) and/or aluminum (Al). The compositions may be configured to regulate the diffusion of metals between a coating and a substrate, which may then influence coating performance, via the formation of an inter-diffusion barrier layer. The inter-diffusion barrier layer may comprise a face-centered cubic phase.

  10. Diffusive Gas Loss from Silica Glass Ampoules at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Palosz, W.

    1998-01-01

    Changes in the pressure of hydrogen, helium and neon due to diffusion through the wall of silica crystal growth ampoules at elevated temperatures were determined experimentally. We show that, while both He- and Ne-losses closely follow conventional model of diffusive gas permeation through the wall, hydrogen losses, in particular at low fill pressures, can be much larger. This is interpreted in terms of the high solubility of hydrogen in silica glasses.

  11. Intrinsic relationship between electronic structures and phase transition of SrBi{sub 2−x}Nd{sub x}Nb{sub 2}O{sub 9} ceramics from ultraviolet ellipsometry at elevated temperatures

    SciTech Connect

    Duan, Z. H.; Jiang, K.; Xu, L. P.; Li, Y. W.; Hu, Z. G. Chu, J. H.

    2014-02-07

    The ferroelectric orthorhombic to paraelectric tetragonal phase transition of SrBi{sub 2−x}Nd{sub x}Nb{sub 2}O{sub 9} (x = 0, 0.05, 0.1, and 0.2) layer-structured ceramics has been investigated by temperature-dependent spectroscopic ellipsometry. Based on the analysis of dielectric functions from 0 to 500 °C with double Tauc-Lorentz dispersion model, the interband transitions located at ultraviolet region have shown an abrupt variation near the Curie temperature. The changes of dielectric functions are mainly due to the thermal-optical and/or photoelastic effect. Moreover, the characteristic alteration in interband transitions can be ascribed to distortion of NbO{sub 6} octahedron and variation of hybridization between Bi 6s and O 2p states during the structure transformation.

  12. Elevated-temperature fracture resistances of monolithic and composite ceramics using chevron-notched bend tests

    NASA Technical Reports Server (NTRS)

    Ghosh, Asish; Jenkins, Michael G.; Ferber, Mattison K.; Peussa, Jouko; Salem, Jonathan A.

    1992-01-01

    The quasi-static fracture behaviors of monolithic ceramics (SiC, Si3N4, MgAl2O4), self-reinforced monoliths (acicular grained Si3N4, acicular grained mullite), and ceramic matrix composites (SiC whisker/Al2O3 matrix, TiB2 particulate/SiC matrix, SiC fiber/CVI SiC matrix, Al2O3 fiber/CVI SiC matrix) were measured over the temperature range of 20 to 1400 C. The chevron notched, bend bar test geometry was essential for characterizing the elevated temperature fracture resistances of this wide range of quasi-brittle materials during stable crack growth. Fractography revealed the differences in the fracture behavior of the different materials at the various temperatures. The fracture resistances of the self-reinforced monoliths were comparable to those of the composites and the fracture mechanisms were found to be similar at room temperature. However at elevated temperatures the differences of the fracture behavior became apparent where the superior fracture resistance of the self-reinforced monoliths were attributed to the minor amounts of glassy, intergranular phases which were often more abundant in the composites and affected the fracture behavior when softened by elevated temperatures.

  13. Kinetics of HMX and Phase Transitions: Effects of Grain Size at Elevated Temperature

    SciTech Connect

    Saw, C K

    2002-06-13

    To date a global kinetic rate law has not been written to accurately describe solid-solid phase transformations of HMX and TATB where contributions from grain size effects, binder contents, and impurity levels are explicitly defined. Our recent work presented at the 2001 SCCM topical APS meeting, Atlanta, GA, demonstrated one can not confidently use the second harmonic generation (SHG) diagnostic to study energetic material phase transitions where non-uniform grain size distributions are present. For example, in HMX, the early arrival of SHG before the XRD in the SHG/XRD simultaneous high temperature experiment clearly indicates the partial molecular conversion from centrosymmetric to non-centrosymmetric without any structural changes as exhibit by the XRD pattern. This conversion is attributed to the changes of the surface molecules due to the differences in potential between the surface and the bulk. The present paper reports on accurate XRD measurements following changes of {beta}-HMX to {delta}-HMX at elevated temperature. The results are compared for sample with 2 different grain sizes for HMX. We report accurate temperature dependent lattice parameters and hence volume and linear thermal expansion coefficients along each crystallographic axis. We have also conducted kinetic studies of the behavior of 2 grain-sizes of HMX and concluded that their kinetics, are drastically different.

  14. Composite structural materials. [aircraft structures

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1980-01-01

    The use of filamentary composite materials in the design and construction of primary aircraft structures is considered with emphasis on efforts to develop advanced technology in the areas of physical properties, structural concepts and analysis, manufacturing, and reliability and life prediction. The redesign of a main spar/rib region on the Boeing 727 elevator near its actuator attachment point is discussed. A composite fabrication and test facility is described as well as the use of minicomputers for computer aided design. Other topics covered include (1) advanced structural analysis methids for composites; (2) ultrasonic nondestructive testing of composite structures; (3) optimum combination of hardeners in the cure of epoxy; (4) fatigue in composite materials; (5) resin matrix characterization and properties; (6) postbuckling analysis of curved laminate composite panels; and (7) acoustic emission testing of composite tensile specimens.

  15. Comparative performance of geopolymers made with metakaolin and fly ash after exposure to elevated temperatures

    SciTech Connect

    Kong, Daniel L.Y.; Sanjayan, Jay G. Sagoe-Crentsil, Kwesi

    2007-12-15

    This paper presents the results of a study on the effect of elevated temperatures on geopolymers manufactured using metakaolin and fly ash of various mixture proportions. Both types of geopolymers (metakaolin and fly ash) were synthesized with sodium silicate and potassium hydroxide solutions. The strength of the fly ash-based geopolymer increased after exposure to elevated temperatures (800 deg. C). However, the strength of the corresponding metakaolin-based geopolymer decreased after similar exposure. Both types of geopolymers were subjected to thermogravimetric, scanning electron microscopy and mercury intrusion porosimetry tests. The paper concludes that the fly ash-based geopolymers have large numbers of small pores which facilitate the escape of moisture when heated, thus causing minimal damage to the geopolymer matrix. On the other hand, metakaolin geopolymers do not possess such pore distribution structures. The strength increase in fly ash geopolymers is also partly attributed to the sintering reactions of un-reacted fly ash particles.

  16. Performance of MOV Stem Lubricants at Elevated Temperatures

    SciTech Connect

    DeWall, Kevin George; Nitzel, Michael Everett; Watkins, John Clifford

    2001-07-01

    This paper documents the results of recent tests sponsored by the U. S. Nuclear Regulatory Commission (NRC) and performed by the Idaho National Engineering and Environmental Laboratory (INEEL). These tests address the effectiveness of the lubricant used on the threaded portion of the valve stem, where the stem nut turns on the stem. Recent testing indicates that an elevated temperature environment can lead to significant increases in the friction coefficient at the stem/stem-nut interface. Most valve actuator qualification tests are performed at room temperature. Similarly, in-service tests are run at ambient plant temperatures, usually 70 to 100°F. Since design conditions can lead to valve operating temperatures in the 200 to 300°F range, it is important to know whether a temperature-induced increase in friction at the stem/stem-nut interface will prevent the required operation of critical valves. Lubricant aging is another phenomenon that might have deleterious effects on the thrust output of a valve actuator. Laboratory experience and field experience both indicate that after long periods in elevated temperature environments, the lubricants may lose their lubrication qualities. The scope of the current test program includes testing of five different lubricants on four different valve stems. Pending completion of the testing, results of the tests conducted using two of the four stems are discussed. The test series included collection of baseline data at room temperature, single step temperature tests where the temperature of the test setup was elevated directly to 250°F, and step testing where the temperature was elevated in steps to 130, 190, and 250°F, then returned to 70°F. All greases tested showed evidence of physical change after elevated temperature tests. Except for one particular lubricant, all of the greases tested showed increased coefficients of friction at elevated temperatures. Numerous other preliminary conclusions are presented

  17. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Loewy, R.; Wiberley, S. E.

    1986-01-01

    Overall emphasis is on basic long-term research in the following categories: constituent materials, composite materials, generic structural elements, processing science technology; and maintaining long-term structural integrity. Research in basic composition, characteristics, and processing science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to present and future problems. Detailed descriptions of the progress achieved in the various component parts of this comprehensive program are presented.

  18. Electrospun melamine resin-based multifunctional nonwoven membrane for lithium ion batteries at the elevated temperatures

    NASA Astrophysics Data System (ADS)

    Wang, Qingfu; Yu, Yong; Ma, Jun; Zhang, Ning; Zhang, Jianjun; Liu, Zhihong; Cui, Guanglei

    2016-09-01

    A flame retardant and thermally dimensional stable membrane with high permeability and electrolyte wettability can overcome the safety issues of lithium ion batteries (LIBs) at elevated temperatures. In this work, a multifunctional thermoset nonwoven membrane composed of melamine formaldehyde resin (MFR) nano-fibers was prepared by a electro-spinning method. The resultant porous nonwoven membrane possesses superior permeability, electrolyte wettability and thermally dimensional stability. Using the electrospun MFR membrane, the LiFePO4/Li battery exhibits high safety and stable cycling performance at the elevated temperature of 120 °C. Most importantly, the MFR membrane contains lone pair electron in the nitrogen element, which can chelate with Mn2+ ions and suppress their transfer across the separator. Therefore, the LiMn2O4/graphite cells with the electrospun MFR multifunctional membranes reveal an improved cycle performance even at high temperature. This work demonstrated that electrospun MFR is a promising candidate material for high-safety separator of LIBs with stable cycling performance at elevated temperatures.

  19. Complexation of neptunium(V) with fluoride in aqueous solutions at elevated temperatures

    SciTech Connect

    Tian, Guoxin; Rao, Linfeng; Xia, Yuanxian; Friese, Judah I.

    2009-02-01

    Over the past several decades, the production and testing of nuclear weapons in the U.S. have created significant amounts of high-level nuclear wastes (HLW) that are currently stored in underground tanks across the U.S. DOE (Department of Energy) sites. Eventually, the HLW will be made into the waste form and disposed of in geological repositories for HLW. Among the radioactive materials, neptunium is of great concern in the post-closure chemical environment in the repository because of the long half-life of 237Np (2.14•106 years) and the high mobility of Np(V), the most stable oxidation state of neptunium. It is estimated that 237Np, together with 129I and 99Tc, will be the major contributors to the potential total annual dose from the repository beyond 10000 years [1]. Due to the high radiation energy released from the HLW, the postclosure repository is expected to remain at elevated temperatures for thousands of years [1]. If the waste package is breached and becomes in contact with groundwater, neptunium, as well as other radioactive materials will be in aqueous solutions at elevated temperatures. Interactions of radioactive materials with the chemical components in groundwater play an important role in determining their migration in the repository. To predict the migration behavior of neptunium, it is necessary to have sufficient and reliable thermodynamic data on its complexation with the ligands that are present in the groundwater of the repository (e.g., OH–, F–, SO42– ,PO43– and CO32) at elevated temperatures. However, such data are scarce and scattered for 25°C, and nearly nonexistent for elevated temperatures [2]. To provide reliable thermodynamic data, we have conducted investigations of the complexation of actinides, including thorium, uranium, neptunium and plutonium, at elevated temperatures. Thermodynamic parameters, including formation constants, enthalpy and heat capacity of complexation are experimentally determined. This paper

  20. Mechanical Properties of T650-35/AFR-PE-4 at Elevated Temperatures for Lightweight Aeroshell Designs

    NASA Technical Reports Server (NTRS)

    Whitley, Karen S.; Collins, TImothy J.

    2006-01-01

    Considerable efforts have been underway to develop multidisciplinary technologies for aeroshell structures that will significantly increase the allowable working temperature for the aeroshell components, and enable the system to operate at higher temperatures while sustaining performance and durability. As part of these efforts, high temperature polymer matrix composites and fabrication technologies are being developed for the primary load bearing structure (heat shield) of the spacecraft. New high-temperature resins and composite material manufacturing techniques are available that have the potential to significantly improve current aeroshell design. In order to qualify a polymer matrix composite (PMC) material as a candidate aeroshell structural material, its performance must be evaluated under realistic environments. Thus, verification testing of lightweight PMC's at aeroshell entry temperatures is needed to ensure that they will perform successfully in high-temperature environments. Towards this end, a test program was developed to characterize the mechanical properties of two candidate material systems, T650-35/AFR-PE-4 and T650-35/RP46. The two candidate high-temperature polyimide resins, AFR-PE-4 and RP46, were developed at the Air Force Research Laboratory and NASA Langley Research Center, respectively. This paper presents experimental methods, strength, and stiffness data of the T650-35/AFR-PE-4 material as a function of elevated temperatures. The properties determined during the research test program herein, included tensile strength, tensile stiffness, Poisson s ratio, compressive strength, compressive stiffness, shear modulus, and shear strength. Unidirectional laminates, a cross-ply laminate and two eight-harness satin (8HS)-weave laminates (4-ply and 10-ply) were tested according to ASTM standard methods at room and elevated temperatures (23, 316, and 343 C). All of the relevant test methods and data reduction schemes are outlined along with

  1. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Wiberley, S. E.

    1978-01-01

    The purpose of the RPI composites program is to develop advanced technology in the areas of physical properties, structural concepts and analysis, manufacturing, reliability and life prediction. Concommitant goals are to educate engineers to design and use composite materials as normal or conventional materials. A multifaceted program was instituted to achieve these objectives.

  2. The Thermal Expansion, Elastic and Fracture Properties of Porous Cordierite at Elevated Temperatures

    SciTech Connect

    Shyam, Amit; Lara-Curzio, Edgar; Pandey, Amit; Watkins, Thomas R; More, Karren

    2012-01-01

    The properties that determine the thermal shock resistance in materials are reported for porous cordierite, a leading candidate material for the fabrication of diesel particulate filters. Fracture toughness and slow crack growth tests were performed on test specimens obtained from the walls of diesel particulate filter monolithic substrates using the double-torsion test method at temperatures between 20 C and 900 C. The thermal expansion and elastic properties were characterized between 20 C and 1000 C. The role of the microstructure of porous cordierite in determining its unusual thermal expansion and elevated temperature Young's modulus and fracture toughness are discussed.

  3. Technology for Elevated Temperature Tests of Structural Panels

    NASA Technical Reports Server (NTRS)

    Thornton, E. A.

    1999-01-01

    A technique for full-field measurement of surface temperature and in-plane strain using a single grid imaging technique was demonstrated on a sample subjected to thermally-induced strain. The technique is based on digital imaging of a sample marked by an alternating line array of La2O2S:Eu(+3) thermographic phosphor and chromium illuminated by a UV lamp. Digital images of this array in unstrained and strained states were processed using a modified spin filter. Normal strain distribution was determined by combining unstrained and strained grid images using a single grid digital moire technique. Temperature distribution was determined by ratioing images of phosphor intensity at two wavelengths. Combined strain and temperature measurements demonstrated on the thermally heated sample were DELTA-epsilon = +/- 250 microepsilon and DELTA-T = +/- 5 K respectively with a spatial resolution of 0.8 mm.

  4. Elevated temperature alters carbon cycling in a model microbial community

    NASA Astrophysics Data System (ADS)

    Mosier, A.; Li, Z.; Thomas, B. C.; Hettich, R. L.; Pan, C.; Banfield, J. F.

    2013-12-01

    Earth's climate is regulated by biogeochemical carbon exchanges between the land, oceans and atmosphere that are chiefly driven by microorganisms. Microbial communities are therefore indispensible to the study of carbon cycling and its impacts on the global climate system. In spite of the critical role of microbial communities in carbon cycling processes, microbial activity is currently minimally represented or altogether absent from most Earth System Models. Method development and hypothesis-driven experimentation on tractable model ecosystems of reduced complexity, as presented here, are essential for building molecularly resolved, benchmarked carbon-climate models. Here, we use chemoautotropic acid mine drainage biofilms as a model community to determine how elevated temperature, a key parameter of global climate change, regulates the flow of carbon through microbial-based ecosystems. This study represents the first community proteomics analysis using tandem mass tags (TMT), which enable accurate, precise, and reproducible quantification of proteins. We compare protein expression levels of biofilms growing over a narrow temperature range expected to occur with predicted climate changes. We show that elevated temperature leads to up-regulation of proteins involved in amino acid metabolism and protein modification, and down-regulation of proteins involved in growth and reproduction. Closely related bacterial genotypes differ in their response to temperature: Elevated temperature represses carbon fixation by two Leptospirillum genotypes, whereas carbon fixation is significantly up-regulated at higher temperature by a third closely related genotypic group. Leptospirillum group III bacteria are more susceptible to viral stress at elevated temperature, which may lead to greater carbon turnover in the microbial food web through the release of viral lysate. Overall, this proteogenomics approach revealed the effects of climate change on carbon cycling pathways and other

  5. Grain boundary oxidation and fatigue crack growth at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Liu, H. W.; Oshida, Y.

    1986-01-01

    Fatigue crack growth rate at elevated temperatures can be accelerated by grain boundary oxidation. Grain boundary oxidation kinetics and the statistical distribution of grain boundary oxide penetration depth were studied. At a constant delta K-level and at a constant test temperature, fatigue crack growth rate, da/dN, is a function of cyclic frequency, nu. A fatigue crack growth model of intermittent micro-ruptures of grain boundary oxide is constructed. The model is consistent with the experimental observations that, in the low frequency region, da/dN is inversely proportional to nu, and fatigue crack growth is intergranular.

  6. The elevated temperature behavior of particle reinforced Al matrix composites

    SciTech Connect

    Lloyd, D.J.

    1994-12-31

    The elevated temperature modulus, strength and creep of SiC particle reinforced composites produced by the DURALCAN{trademark} are discussed. It is shown that the reinforcing particles provide an increased modulus over the complete temperature range studied, and the temperature dependence of the composite modulus is controlled by the temperature dependence of the matrix modulus. The composite strength decreases with increasing temperature, reflecting softening of the matrix due to over aging, and as a result, is dependent on the thermal stability of the matrix. The particles provide increased creep resistance, and there are differences between the creep of melt processed composites and those produced by powder metallurgy.

  7. Light thermal structures and materials for high speed flight

    NASA Technical Reports Server (NTRS)

    Thornton, Earl A.

    1992-01-01

    Over the last twenty years, unified viscoplastic constitutive models have evolved to meet this need. These constitutive models provide a means for representing a material's response from the elastic through the plastic range including strain-rate dependent plastic flow, creep, and stress relaxation. Rate-dependent plasticity effects are known to be important at elevated temperatures. The purpose of this paper is to describe computational and experimental research programs underway at the Light Thermal Structures Center focused on the investigation of the response of structures and materials to local heating. In the first part of the paper, finite element thermoviscoplastic analysis is highlighted. In the second part of the paper, the thermal-structures experimental program is outlined.

  8. Description of a system for interlocking elevated temperature mechanical tests

    SciTech Connect

    Schmale, D.T.; Poulter, G.A.

    1995-07-01

    Long term mechanical creep and fatigue testing at elevated temperatures requires reliable systems with safeguards to prevent destruction of equipment, loss of data and negative environmental impacts. Toward this goal, a computer controlled system has been developed and built for interlocking tests run on elevated temperature mechanical test facilities. Sensors for water flow, water pressure, water leakage, temperature, power and hydraulic status are monitored to control specimen heating equipment through solid state relays and water solenoid valves. The system is designed to work with the default interlocks present in the RF generators and mechanical tests systems. Digital hardware consists of two National Instruments 1/0 boards mounted in a Macintosh IIci computer. Software is written in National Instruments LabVIEW. Systems interlocked include two MTS closed loop servo controlled hydraulic test frames, one with an RF generator and one with both an RF generator and a quartz lamp furnace. Control for individual test systems is modularized making the addition of more systems simple. If any of the supporting utilities fail during tests, heating systems, chill water and hydraulics are powered down, minimizing specimen damage and eliminating equipment damage. The interlock control is powered by an uninterruptible power supply. Upon failure the cause is documented in an ASCII file.

  9. Oxidative stress causes coral bleaching during exposure to elevated temperatures

    NASA Astrophysics Data System (ADS)

    Lesser, M. P.

    1997-07-01

    Elevated temperatures and solar ultraviolet (UV) radiation have been implicated as recent causes for the loss of symbiotic algae (i.e., bleaching) in corals and other invertebrates with photoautotrophic symbionts. One hypothesized mechanism of coral bleaching involves the production of reduced oxygen intermediates, or toxic oxygen, in the dinoflagellate symbionts and host tissues that subsequently causes cellular damage and expulsion of symbionts. Measurements of photosynthesis in the Caribbean coral Agaricia tenuifolia, taken during temperature-induced stress and exposure to full solar radiation, showed a decrease in photosynthetic performance followed by bleaching. Exposure of corals to exogenous antioxidants that scavenge reactive oxygen species during temperature-induced stress improves maximum photosynthetic capacity to rates indistinguishable from corals measured at the ambient temperature of their site of collection. Additionally, these antioxidants prevent the coral from " bleaching " and affect the mechanism of symbiont loss from the coral host. These observations confirm a role for oxidative stress, whether caused by elevated temperatures or exposure to UV radiation, in the bleaching phenomenon.

  10. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1982-01-01

    The promise of filamentary composite materials, whose development may be considered as entering its second generation, continues to generate intense interest and applications activity. Fiber reinforced composite materials offer substantially improved performance and potentially lower costs for aerospace hardware. Much progress has been achieved since the initial developments in the mid 1960's. Rather limited applications to primary aircraft structure have been made, however, mainly in a material-substitution mode on military aircraft, except for a few experiments currently underway on large passenger airplanes in commercial operation. To fulfill the promise of composite materials completely requires a strong technology base. NASA and AFOSR recognize the present state of the art to be such that to fully exploit composites in sophisticated aerospace structures, the technology base must be improved. This, in turn, calls for expanding fundamental knowledge and the means by which it can be successfully applied in design and manufacture.

  11. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1984-01-01

    Progress is reported in studies of constituent materials composite materials, generic structural elements, processing science technology, and maintaining long-term structural integrity. Topics discussed include: mechanical properties of high performance carbon fibers; fatigue in composite materials; experimental and theoretical studies of moisture and temperature effects on the mechanical properties of graphite-epoxy laminates and neat resins; numerical investigations of the micromechanics of composite fracture; delamination failures of composite laminates; effect of notch size on composite laminates; improved beam theory for anisotropic materials; variation of resin properties through the thickness of cured samples; numerical analysis composite processing; heat treatment of metal matrix composites, and the RP-1 and RP2 gliders of the sailplane project.

  12. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1979-01-01

    A multifaceted program is described in which aeronautical, mechanical, and materials engineers interact to develop composite aircraft structures. Topics covered include: (1) the design of an advanced composite elevator and a proposed spar and rib assembly; (2) optimizing fiber orientation in the vicinity of heavily loaded joints; (3) failure mechanisms and delamination; (4) the construction of an ultralight sailplane; (5) computer-aided design; finite element analysis programs, preprocessor development, and array preprocessor for SPAR; (6) advanced analysis methods for composite structures; (7) ultrasonic nondestructive testing; (8) physical properties of epoxy resins and composites; (9) fatigue in composite materials, and (10) transverse thermal expansion of carbon/epoxy composites.

  13. Composite Structural Materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberly, S. E.

    1984-01-01

    The development and application of filamentary composite materials, is considered. Such interest is based on the possibility of using relatively brittle materials with high modulus, high strength, but low density in composites with good durability and high tolerance to damage. Fiber reinforced composite materials of this kind offer substantially improved performance and potentially lower costs for aerospace hardware. Much progress has been made since the initial developments in the mid 1960's. There were only limited applied to the primary structure of operational vehicles, mainly as aircrafts.

  14. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1982-01-01

    Research in the basic composition, characteristics, and processng science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to problems. Detailed descriptions of the progress achieved in the various component parts of his program are presented.

  15. Materials and structures technology

    NASA Technical Reports Server (NTRS)

    Signorelli, R. A.; Glasgow, T. K.; Halford, G. R.; Levine, S. R.

    1979-01-01

    Materials and structures performance limitations, particularly for the hot section of the engine in which these limitations limit the life of components, are considered. Failure modes for components such as blades, vanes, and combustors and how they are affected by the environment for such components are discussed. Methods used to improve the materials used for such components are: (1) application of directional structures to turbine components for high strength at high temperatures; (2) improved coatings to increase oxidation and corrosion resistance; (3) increase strength and stiffness with reduced weight by applying higher specific properties of composite materials; and (4) cost effective processing such as near net shape powder methods applied to disks. Life prediction techniques developed to predict component life accurately in advance of service and progress in improving the intermediate and cold section components of turbine engines are covered.

  16. Elevated temperature fracture of RS/PM aluminum alloy 8009

    NASA Technical Reports Server (NTRS)

    Porr, William C., Jr.; Yang, Leng; Gangloff, Richard P.

    1991-01-01

    The fracture behavior of advanced powder metallurgy Al-Fe-V-Si alloy 8009 (previously called FVS0812) is being characterized under monotonic loads, as a function of temperature. Particular attention is focused on contributions to the fracture mechanism from the fine grained dispersoid strengthened microstructure, dissolved solute from rapid solidification, and the moist air environment. Time-dependent crack growth is characterized in advanced aluminum alloys at elevated temperatures with the fracture mechanics approach, and cracking mechanisms are examined with a metallurgical approach. Specific tasks were to obtain standard load crack growth experimental information from a refined testing system; to correlate crack growth kinetics with the j-integral and time dependent C(sub t)(t); and to investigate the intermediate temperature embrittlement of 8009 alloy in order to understand crack growth mechanisms.

  17. Thermodynamics of Neptunium (V) Complexes with Phosphate at Elevated Temperatures

    SciTech Connect

    Xia, Y.; Friese, Judah I.; Bachelor, Paula P.; Moore, Dean A.; Rao, Linfeng

    2009-06-01

    Abstract – The complexation of Np(V) with phosphate at elevated temperatures was studied by a synergistic extraction method. A mixed buffer solution of TRIS and MES was used to maintain an appropriate pH value during the distribution experiments. The distribution ratio of Np(V) between the organic and aqueous phases was found to decrease as the concentrations of phosphate were increased. Stability constants of the 1:1 and 1:2 Np(V)-HPO42- complexes, dominant in the aqueous phase under the experimental conditions, were calculated from the effect of [HPO42-] on the distribution ratio. The thermodynamic parameters including enthalpy and entropy of complexation between Np(V) and HPO42- at 25o C – 55o C were calculated by the temperature coefficient method.

  18. Microchip Electrophoresis at Elevated Temperatures and High Separation Field Strengths

    PubMed Central

    Mitra, Indranil; Marczak, Steven P.; Jacobson, Stephen C.

    2014-01-01

    We report free-solution microchip electrophoresis performed at elevated temperatures and high separation field strengths. We used microfluidic devices with 11-cm long separation channels to conduct separations at temperatures between 22 (ambient) and 45 °C and field strengths from 100 to 1000 V/cm. To evaluate separation performance, N-glycans were used as a model system and labeled with 8-aminopyrene-1,3,6-trisulfonic acid to impart charge for electrophoresis and render them fluorescent. Typically, increased diffusivity at higher temperatures leads to increased axial dispersion and poor separation performance; however, we demonstrate that sufficiently high separation field strengths can be used to offset the impact of increased diffusivity in order to maintain separation efficiency. Efficiencies for these free-solution separations are the same at temperatures of 25, 35, and 45 °C with separation field strengths ≥500 V/cm. PMID:24114979

  19. Young's modulus of cement paste at elevated temperatures

    SciTech Connect

    Odelson, Joshua B.; Kerr, Elizabeth A.; Vichit-Vadakan, Wilasa . E-mail: WVichitVadakan@ctlgroup.com

    2007-02-15

    Calcium silicate hydrate is a porous hydrate that is sensitive to temperature and readily loses strength at elevated temperatures. Mechanical and chemical changes in the microstructure, due to escaping water, can significantly affect the mechanical properties, but these changes occur over different temperature ranges. By measuring Young's modulus as a function of temperature using the dynamic mechanical analyzer, the temperature range in which the greatest change in stiffness occurs can be identified. Additional mineralogy, pore size distribution, and composition analysis from high temperature X-ray diffraction, nitrogen sorption, and thermogravimetric analysis will demonstrate the changes in the microstructure. The results demonstrate that over 90% of the loss in stiffness occurs below 120 deg. C. Therefore, the damage is due to microcracking caused by pore water expansion and evaporation and not the change in mineralogy or composition. More damage, as indicated by greater loss in stiffness, occurs in stiffer and less permeable samples where higher stresses can develop.

  20. Tolerance of LSS plant component to elevated temperatures.

    PubMed

    Ushakova, S A; Tikhomirov, A A

    2002-06-01

    Stability of LSS based on biological regeneration of water, air and food subject to damaging factors is largely dependent on the behavior of the photosynthesizing component represented, mainly, by higher plants. The purpose of this study is to evaluate the tolerance of uneven-aged wheat and radish cenoses to temperature effects different in time and value. Estimation of thermal tolerance of plants demonstrated that exposure for 20 h to the temperature increasing to 45 degrees C brought about irreversible damage both in photosynthetic processes (up to 80% of initial value) and the processes of growth and development. Kinetics of visible photosynthesis during exposure to elevated temperatures can be used to evaluate critical exposure time within the range of which the damage of metabolic processes is reversible. With varying light intensity and air temperature it is possible to find a time period admissible for the plants to stay under adverse conditions without considerable damage of metabolic processes. PMID:12053940

  1. Complexation of Neptunium(V) with Fluoride at Elevated Temperatures

    SciTech Connect

    Rao, Linfeng; Tian, Guoxin; Xia, Yuanxian; Friese, Judah I.

    2008-06-16

    Complexation of neptunium(V) with fluoride at elevated temperatures was studied by spectrophotometry and microcalorimetry. Two successive complexes, NpO{sub 2}F(aq) and NpO{sub 2}F{sub 2}{sup -}, were identified by spectrophotometry in the temperature range of 10-70 C. Thermodynamic parameters, including the equilibrium constants and enthalpy of complexation between Np(V) and fluoride at 10-70 C were determined. Results show that the complexation of Np(V) with fluoride is endothermic and that the complexation is enhanced by the increase in temperature - a two-fold increase in the stability constants of NpO{sub 2}F(aq) and more than five-fold increase in the stability constants of NpO{sub 2}F{sub 2}{sup -} as the temperature is increased from 10 to 70 C.

  2. Room Temperature and Elevated Temperature Composite Sandwich Joint Testing

    NASA Technical Reports Server (NTRS)

    Walker, Sandra P.

    1998-01-01

    Testing of composite sandwich joint elements has been completed to verify the strength capacity of joints designed to carry specified running loads representative of a high speed civil transport wing. Static tension testing at both room and an elevated temperature of 350 F and fatigue testing at room temperature were conducted to determine strength capacity, fatigue life, and failure modes. Static tension test results yielded failure loads above the design loads for the room temperature tests, confirming the ability of the joint concepts tested to carry their design loads. However, strength reductions as large as 30% were observed at the elevated test temperature, where all failure loads were below the room temperature design loads for the specific joint designs tested. Fatigue testing resulted in lower than predicted fatigue lives.

  3. EROSION OF ELEVATED TEMPERATURE CORROSION SCALES ON METALS

    SciTech Connect

    Maasberg, J.A.; Levy, A.V.

    1981-05-01

    Combined erosion-corrosion poses a considerable problem to the design of long lifetime metallic components in energy conversion systems. To gain some insight into this problem, scales were formed on stainless steel at elevated temperature and subsequently were eroded at room temperature to determine the nature of the erosion rates and the mechanism of scale removal. Thin corrosion scales were formed on 310 stainless steel and an experimental Fe-18Cr-5Al-1Hf alloy at high temperatures (9ooo and 980°C) in gas mixtures with various levels of oxygen and combined oxygen-sulfur. The corroded specimens were eroded at room temperature in an air-solid particle stream using 50{micro}m SiC at 60 ms{sup -1}. The conditions of the corrosive exposures, the rates of erosion of these scales and the microscopic appearance of the eroded surface were correlated to determine the mechanism of thin scale erosion.

  4. Friction Properties of Molybdenum Alloyed Steel at Elevated Temperatures

    SciTech Connect

    Li Jianliang; Xiong Dangsheng; Wu Hongyan

    2011-01-17

    The high-temperature properties of steel surface can be improved by molybdenum surface alloying. Molybdenzing was carried out on carbon steel in the multi-function double glow plasma surface alloying furnace. The friction and wear tests were conducted on a high temperature ball-on-disk tribometer under the temperature of 25 deg. C{approx}600 deg. C. The contents of alloy element varied with alloyed layer were detected by SEM attached with EDS. The molybdenized layer is composed of the deposited layer and diffused layer. The micro-hardness of alloyed layer decreases from HV650 on the top layer to HV240. The friction coefficient of molybdenized layer decreases from 0.5{approx}0.6 to 0.2{approx}0.3 and wear rate decreases by 20% at elevated temperature after molybdenizing.

  5. Compressive Strength of Stainless-Steel Sandwiches at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Mathauser, Eldon E.; Pride, Richard A.

    1959-01-01

    Experimental results are presented from crippling tests of stainless-steel sandwich specimens in the temperature range from 80 F to 1,200 F. The specimens included resistance-welded 17-7 PH stainless-steel sandwiches with single-corrugated cores, type 301 stainless-steel sandwiches with double-corrugated cores, and brazed 17-7 PH stainless-steel sandwiches with honeycomb cores. The experimental strengths are compared with predicted buckling and crippling strengths. The crippling strengths were predicted from the calculated maximum strength of the individual plate elements of the sandwiches and from a correlation procedure which gives the elevated-temperature crippling strength when the experimental room-temperature crippling strengths are known. Photographs of some of the tested specimens are included to show the modes of failure.

  6. Tolerance of LSS Plant Component to Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Ushakova, S. A.; Tikhomirov, A. A.

    2002-06-01

    Stability of LSS based on biological regeneration of water, air and food subject to damaging factors is largely dependent on the behavior of the photosynthesizing component represented, mainly, by higher plants. The purpose of this study is to evaluate the tolerance of uneven-aged wheat and radish cenoses to temperature effects different in time and value. Estimation of thermal tolerance of plants demonstrated that exposure for 20 h to the temperature increasing to 45°C brought about irreversible damage both in photosynthetic processes (up to 80% of initial value) and the processes of growth and development. Kinetics of visible photosynthesis during exposure to elevated temperatures can be used to evaluate critical exposure time within the range of which the damage of metabolic processes is reversible. With varying light intensity and air temperature it is possible to find a time period admissible for the plants to stay under adverse conditions without considerable damage of metabolic processes.

  7. Hydrologic property alterations due to elevated temperatures at Yucca Mountain

    SciTech Connect

    Flint, A.L.; Nash, M.H.; Nash, M.S.

    1994-12-31

    Yucca Mountain is currently being evaluated as a potential site for a high level nuclear waste repository. The pre-emplacement hydrologic properties of the rock are important in determining the suitability of the site; however, post emplacement thermal loads and associated drying may permanently alter the character of the rock. A preliminary study was undertaken to determine the effects of elevated temperatures on hydrologic properties of the welded Topopah Spring member of the Paintbrush Tuff and a zeolitic, nonwelded tuff from the Tuffaceous Beds of Calico Hills. Rock outcrop samples were collected and dried in the laboratory at different temperatures (up to 400 degrees C). Hydrologic and physical properties -were tested before and after each of the drying cycles.

  8. Elevated temperature crack growth in aluminum alloys: Tensile deformation of 2618 and FVS0812 aluminum alloys

    NASA Technical Reports Server (NTRS)

    Leng, Yang; Gangloff, Richard P.

    1990-01-01

    Understanding the damage tolerance of aluminum alloys at elevated temperatures is essential for safe applications of advanced materials. The objective of this project is to investigate the time dependent subcritical cracking behavior of powder metallurgy FVS0812 and ingot metallurgy 2618 aluminum alloys at elevated temperatures. The fracture mechanics approach was applied. Sidegrooved compact tension specimens were tested at 175, 250, and 316 C under constant load. Subcritical crack growth occurred in each alloy at applied stress intensity levels (K) of between about 14 and 25 MPa/m, well below K (sub IC). Measured load, crack opening displacement and displacement rate, and crack length and growth rate (da/dt) were analyzed with several continuum fracture parameters including, the C-integral, C (sub t), and K. Elevated temperature growth rate data suggest that K is a controlling parameter during time dependent cracking. For FVS0812, da/dt is highest at 175 C when rates are expressed as a function of K. While crack growth rate is not controlled by C (sub t) at 175 C, da/dt appears to better correlate with C (sub t) at higher temperatures. Creep brittle cracking at intermediate temperatures, and perhaps related to strain aging, is augmented by time dependent transient creep plasticity at higher temperatures. The C (sub t) analysis is, however, complicated by the necessity to measure small differences in the elastic crack growth and creep contributions to the crack opening displacement rate. A microstructural study indicates that 2618 and FVS0812 are likely to be creep brittle materials, consistent with the results obtained from the fracture mechanics study. Time dependent crack growth of 2618 at 175 C is characterized by mixed transgranular and intergranular fracture. Delamination along the ribbon powder particle boundaries occurs in FVS0812 at all temperatures. The fracture mode of FVS0812 changes with temperature. At 175 C, it is characterized as dimpled rupture

  9. Mechanical properties of long carbon fiber reinforced thermoplastic (LFT) at elevated temperature

    NASA Astrophysics Data System (ADS)

    Wang, Qiushi

    Long fiber reinforced thermoplastics (LFT) possess high specific modulus and strength, superior damage tolerance and fracture toughness and have found increasing use in transportation, military, and aerospace applications. However, one of the impediments to utilizing these materials is the lack of performance data in harsh conditions, especially at elevated temperature. In order to quantify the effect of temperature on the mechanical properties of carbon fiber reinforced thermoplastic composites, carbon fiber PAA composite plates containing 20% and 30% carbon fiber were produced using extrusion/compression molding process and tested at three representative temperatures, room temperature (RT 26°C), middle temperature (MID 60°C) and glass transition temperature (Tg 80°C). A heating chamber was designed and fabricated for the testing at elevated temperature. As temperature increases, flexural modulus, flexural strength, tensile modulus and tensile strength decrease. The highest reduction observed in stiffness (modulus) values of 30% CF/PAA at Tg in the 00 orientation is 75%. The reduction values were larger for the transverse (perpendicular to flow direction) samples than the longitudinal (flow direction) samples. The property reduction in 30% CF/PAA is larger than 20% CF/PAA. Furthermore, an innovative method was developed to calculate the fiber content in carbon fiber reinforced composites by burning off the neat resin and sample in a tube furnace. This method was proved to be accurate (within 1.5 wt. % deviation) by using burning off data obtained from CF/Epoxy and CF/Vinyl Ester samples. 20% and 30% carbon/PAA samples were burned off and carbon fiber content was obtained using this method. The results of the present study will be helpful in determining the end-user applications of these composite materials. Keywords: Long Carbon Fibers, Elevated Temperature, Mechanical Properties, Burn off Test.

  10. Zeta Potential in Intact Natural Carbonates at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Al-Mahrouqi, D.; Vinogradov, J.; Jackson, M.

    2015-12-01

    Measurements of zeta potential have been used to monitor subsurface flows in many natural brine systems. Numerous studies report zeta potentials in carbonates using crushed samples at low ionic strength and laboratory temperatures. However, natural brines have much higher salinity; moreover, temperatures are considerably higher in many subsurface settings. The variation of zeta potentials with temperature has not been examined in natural carbonates. We report zeta potential values interpreted from streaming potential measurements in two intact carbonate rock samples, saturated with artificial brines at elevated temperatures. We measure streaming potential using an experimental set-up that incorporates in-situ measurements of saturated rock conductivity, brine temperature, brine pH, brine electrical conductivity, pressure difference and voltage at temperatures up to 120oC. The streaming potential measurements are complemented with brine effluent studies. We find that the interpreted zeta potential is negative and decreases in magnitude with increasing temperature at low ionic strength (0.01M) and independent of temperature at high ionic strength (0.5M); consistent with published zeta potential in intact natural sandstones. The concentration of Ca2+ (main potential determining ion) also decreases with temperature at low ionic strength, but remains constant at high ionic strength. The temperature dependence of the zeta potential is consistent between two different natural carbonate samples and can be explained by the temperature dependence of pCa2+. We suggest that zeta potential of carbonate is independent of temperature or pH when pCa2+ remains constant. A linear variation of pH vs. pCa2+ is exhibited, at ambient and elevated temperatures, when pCa2+ is allowed to change with pH. This linear variation explains the numerous published data that shows apparent relationship between zeta potential of carbonates and pH.

  11. Capacity fade of Sony 18650 cells cycled at elevated temperatures. Part II. Capacity fade analysis

    NASA Astrophysics Data System (ADS)

    Ramadass, P.; Haran, Bala; White, Ralph; Popov, Branko N.

    A complete capacity fade analysis was carried out for Sony 18650 cells cycled at elevated temperatures. The major causes of capacity loss were identified and a complete capacity fade balance was carried out to account for the total capacity loss of Li-ion battery as a function of cycle number and temperature. The three most significant parameters that cause capacity loss were loss of secondary active material (LiCoO 2/carbon) and primary active material (Li +) and the rate capability losses. Intrinsic capacity measurements for both positive and negative electrode has been used to estimate the capacity loss due to secondary active material and a charge balance gives the capacity lost due to primary active material (Li +). Capacity fade has been quantified with secondary active material loss dominating the other losses.

  12. On the interaction of water-soluble binders and nano silicon particles: alternative binder towards increased cycling stability at elevated temperatures.

    PubMed

    Klamor, S; Schröder, M; Brunklaus, G; Niehoff, P; Berkemeier, F; Schappacher, F M; Winter, M

    2015-02-28

    Silicon based composites are among the most promising negative electrodes for lithium ion battery applications due to their high theoretical capacities. One major drawback of silicon based anodes are their large volume changes during lithiation and delithiation. Although many efforts have been made in view of new binder materials and improved electrolytes, the resulting battery cell suffers from severe capacity fading at ambient or elevated temperatures, respectively. The strong reactivity with the electrolyte is considered to be responsible for the reduced cycle life at elevated temperatures. In this work we introduce silicon composite anodes with a novel composition based on a gellan gum binder material that show an improved cycling performance at ambient temperature and at 60 °C. To elucidate the influence of the binder material, we investigated the structure of the silicon based composite anodes in order to understand the nature of the interaction of the gellan gum based binder polymers with the silicon particles in comparison with a common CMC binder. Also the influence of the choice of binder on the interactions at the interface between electrode surface and electrolyte were studied. A combination of powerful techniques including solid state NMR, TEM and EELS, XPS as well as FTIR were applied. PMID:25623421

  13. The Effects of Elevated Temperatures on the Response of Resins Under Dynamic and Static Loadings

    NASA Technical Reports Server (NTRS)

    Gilat, Amos

    2005-01-01

    The overall objective of the research is to experimentally study the combined effects of temperature and strain rate on the response of two resins that are commonly used for the matrix material in composites. The resins are loaded at various temperatures in shear and in tension over a wide range of strain rates. These two types of loadings provide an opportunity to examine also the effect that temperature might have on the effects of the hydrostatic stress component on the material response. The experimental data provide the information needed for NASA scientists for the development of a nonlinear, strain rate, and temperature dependent deformation and strength models for composites that can subsequently be used in design. This year effort was directed into the development and testing of the epoxy resin at elevated temperatures. Two types of epoxy resins were tested in shear at high strain rates of about 10(exp-4)/s and elevated temperatures of 50 and 8OC. The results show that the temperature significantly affects the response of epoxy.

  14. Code qualification of structural materials for AFCI advanced recycling reactors.

    SciTech Connect

    Natesan, K.; Li, M.; Majumdar, S.; Nanstad, R.K.; Sham, T.-L.

    2012-05-31

    This report summarizes the further findings from the assessments of current status and future needs in code qualification and licensing of reference structural materials and new advanced alloys for advanced recycling reactors (ARRs) in support of Advanced Fuel Cycle Initiative (AFCI). The work is a combined effort between Argonne National Laboratory (ANL) and Oak Ridge National Laboratory (ORNL) with ANL as the technical lead, as part of Advanced Structural Materials Program for AFCI Reactor Campaign. The report is the second deliverable in FY08 (M505011401) under the work package 'Advanced Materials Code Qualification'. The overall objective of the Advanced Materials Code Qualification project is to evaluate key requirements for the ASME Code qualification and the Nuclear Regulatory Commission (NRC) approval of structural materials in support of the design and licensing of the ARR. Advanced materials are a critical element in the development of sodium reactor technologies. Enhanced materials performance not only improves safety margins and provides design flexibility, but also is essential for the economics of future advanced sodium reactors. Code qualification and licensing of advanced materials are prominent needs for developing and implementing advanced sodium reactor technologies. Nuclear structural component design in the U.S. must comply with the ASME Boiler and Pressure Vessel Code Section III (Rules for Construction of Nuclear Facility Components) and the NRC grants the operational license. As the ARR will operate at higher temperatures than the current light water reactors (LWRs), the design of elevated-temperature components must comply with ASME Subsection NH (Class 1 Components in Elevated Temperature Service). However, the NRC has not approved the use of Subsection NH for reactor components, and this puts additional burdens on materials qualification of the ARR. In the past licensing review for the Clinch River Breeder Reactor Project (CRBRP) and the

  15. The Deformation of the Multi-Layered Panel of Sheet Metals Under Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Wook; Woo, Dong-Uk

    A Molten Carbonate Fuel Cell (MCFC) stack consists of several layered unit cells. In each unit cell, the stiff structure of the separator plate contains the softer components, such as electrodes. When surface pressure acts on the stack over an extended period of time at elevated temperatures, the stiffness of the separator plate tends to degrade. Moreover, the demands for large electrode area (to increase the electric capacity of a unit cell) and thinner separator plates (to reduce weight) complicate the design of a separator plate with high stiffness. To evaluate the stiffness of the separator plate at elevated temperatures, we design and test a tiny, multi-layered separator plate specimen using a three-point bending tool. To determine the optimal structure of the separator plate, we investigate three design factors: angle, pitch and height. We adopt the Taguchi method to evaluate the experiments, and use finite element analysis to examine the experimental results. Based on these results, pitch is the most effective of these factors. As the pitch narrows, the stiffness of the separator plate increases. Therefore, we propose the pitch factor as a design criterion for the separator plate of the MCFC stack.

  16. Interface degradation in CAS/Nicalon during elevated temperature aging

    SciTech Connect

    Plucknett, K.P.; Cain, R.L.; Lewis, M.H.

    1995-03-01

    A CaO-Al{sub 2}O{sub 3}-SiO{sub 2} (CAS)/Nicalon glass-ceramic matrix composite has been subjected to elevated temperature oxidation heat-treatments between 375 and 1200{degrees}C, for up to 100 hours. Micro- and macro-mechanical properties have been determined by fiber push-down, using a mechanical properties microprobe, and flexure testing, respectively. Aging between 450 and 800{degrees}C results in significant property degradation, with reduced bending modulus and flexure strength, increased fiber sliding stress, and a transition to a purely brittle failure mode. Aging degradation is due to oxidative removal of the carbon interlayer, with the subsequent formation of a silica bond between fiber and matrix. At higher temperatures, carbon is retained due to the formation of a protective silica plug at exposed fiber ends, with the subsequent retention of composite properties. Short duration pre-treatment schedules, at 1000 or 1100{degrees}C, were developed to prevent intermediate temperature property degradation.

  17. Factor Study for the Separator Plate of Mcfc Having Uniform Stiffness at Elevated Temperature

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Wook; Kim, Jung-Hyun; Jun, Joong-Hwan

    A molten carbonate fuel cell (MCFC) is composed of several stacks of unit cells. A unit cell is composed of two electrodes and a matrix that is inserted between separator plates. Separator plates should properly contact the electrodes to reduce the electricity loss arising from contact resistance. To this end, a pressure of about 2 kgf/cm2 is usually applied on the top of the stack, which results in the separator plates being somewhat compacted. Furthermore, the stiffness of the separator plates becomes degraded at elevated temperatures due to softening of the plate materials. Therefore, a nonuniform temperature distribution across the separator plates induced by exothermic reactions of the oxidant and reactant gases leads to a non-uniform plate stiffness. This study has firstly evaluated the change in separator plate stiffness as temperature changes by applying pressure to the plates. Secondly, using the Taguchi method, several design factors that affect stiffness have been investigated to determine which has the most influence. Based on these results, a new design for the separators, which allows for uniform stiffness at elevated temperatures, has been proposed.

  18. Combined Mode I and Mode II Fracture of Plasma-Sprayed Thermal Barrier Coatings at Ambient and Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Zhu, Dongming; Miller, Robert A.

    2003-01-01

    The mode I, mode II, and combined mode I-mode II fracture behavior of ZrO2 - 8wt%Y2O3 thermal barrier coatings was determined in asymmetric flexure loading at both ambient and elevated temperatures. Precracks were introduced in test specimens using the single-edge-v-notched beam (SEVNB) method incorporated with final diamond polishing to achieve sharp crack tips. A fracture envelope of KI versus KII was determined for the coating material at ambient and elevated temperatures. Propagation angles of fracture as a function of KI/KII were also determined. The mixed-mode fracture behaviors of the coating material were compared with those of monolithic advanced ceramics determined previously. The mixed-mode fracture behavior of the plasma- sprayed thermal barrier coating material was predicted in terms of fracture envelope and propagation angle using mixed-mode fracture theories.

  19. Combined Mode I and Mode II Fracture of Plasma-Sprayed Thermal Barrier Coatings at Ambient and Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Zhu, Dongming; Miller, Robert A.

    2003-01-01

    The mode I, mode II, and combined mode I-mode II fracture behavior of ZrO2- 8wt%Y2O3 thermal barrier coatings was determined in asymmetric flexure loading at both ambient and elevated temperatures. Precracks were introduced in test specimens using the single-edge-v-notched beam (SEVNB) method incorporated with final diamond polishing to achieve sharp crack tips. A fracture envelope of KI versus KII was determined for the coating material at ambient and elevated temperatures. Propagation angles of fracture as a function of K(sub I)/K(sub II) were also determined. The mixed-mode fracture behaviors of the coating material were compared with those of monolithic advanced ceramics determined previously. The mixed-mode fracture behavior of the plasma-sprayed thermal barrier coating material was predicted in terms of fracture envelope and propagation angle using mixed-mode fracture theories.

  20. Concrete Materials and Structures

    SciTech Connect

    Wilby, C.B.

    1991-12-31

    Concrete Materials and Structures provides one of the most comprehensive treatments on the topic of concrete engineering. The author covers a gamut of concrete subjects ranging from concrete mix design, basic reinforced concrete theory, prestressed concrete, shell roofs, and two-way slabs-including a through presentation of Hillerborg`s strip method. Prior to Wilby`s book, the scope of these topics would require at least four separate books to cover. With this new book he has succeeded, quite remarkably, in condensing a fairly complete knowledge of concrete engineering into one single easy-to-carry volume.

  1. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Loewy, Robert G.; Wiberley, Stephen E.

    1987-01-01

    The development and application of composite materials to aerospace vehicle structures which began in the mid 1960's has now progressed to the point where what can be considered entire airframes are being designed and built using composites. Issues related to the fabrication of non-resin matrix composites and the micro, mezzo and macromechanics of thermoplastic and metal matrix composites are emphasized. Several research efforts are presented. They are entitled: (1) The effects of chemical vapor deposition and thermal treatments on the properties of pitch-based carbon fiber; (2) Inelastic deformation of metal matrix laminates; (3) Analysis of fatigue damage in fibrous MMC laminates; (4) Delamination fracture toughness in thermoplastic matrix composites; (5) Numerical investigation of the microhardness of composite fracture; and (6) General beam theory for composite structures.

  2. The elevated temperature erosion behavior of HVOF tungsten carbide cermet coatings

    SciTech Connect

    Wang, B.Q.

    1995-12-31

    A series of elevated temperature erosion tests was carried out on HVOF Wc-17Co cermet coating specimens at 300 C and 450 C at particle velocities of 30 m/s and 60 m/s and at impact angles of 30{degree} and 90{degree}, using bed ashes and fly ashes retrieved from operating CFBC boilers. The elevated temperature erosion behavior of HVOF WC-17Co coatings was compared with those of AISI 1018 steel, and other thermal sprayed coatings including a HVOF 75%Cr{sub 3}C{sub 2}-25%NiCr cermet coating, an arc-sprayed FeCrSiB metallic coating and a flame-sprayed Cr{sub 2}O{sub 3}-6SiO{sub 2}-4Al{sub 2}O{sub 3} ceramic coating. The morphologies of specimens were examined by light microscopy and scanning electron microscopy (SEM). The microhardness of the surface of the specimens was measured. It was found that the hardness of the coatings had no direct relationship with erosion-corrosion wastage and the erosion behavior of coatings is closely related to their microstructure and composition. In general, the coatings with larger splat size, coarse and heterogeneous structure, higher porosity and the presence of craze cracks or inclusions have the higher erosion wastage. However, the effect of microstructure of coatings on the erosion behavior varied with erosion test conditions.

  3. The Mechanical Behavior of a 25Cr Super Duplex Stainless Steel at Elevated Temperature

    NASA Astrophysics Data System (ADS)

    Lasebikan, B. A.; Akisanya, A. R.; Deans, W. F.

    2013-02-01

    Super duplex stainless steel (SDSS) is a candidate material for production tubing in oil and gas wells and subsea pipelines used to transport corrosive hydrocarbon fluids. The suitability of this material for high temperature applications is examined in this article. The uniaxial tensile properties are determined for a 25Cr SDSS over a range of temperature relevant to high pressure-high temperature oil and gas wells. It is shown that there is a significant effect of temperature on the uniaxial tensile properties. Elevated temperature was shown to reduce the Young's modulus and increase the strain hardening index; temperature effects on these two parameters are usually neglected in the design of subsea pipelines and oil well tubulars, and this could lead to wrong predictions of the collapse pressure. The manufacturing process of the super duplex tubular did not lead to significant anisotropy in the hardness and the ultimate tensile and uniaxial yield strengths.

  4. Factors Controlling Elevated Temperature Strength Degradation of Silicon Carbide Composites

    NASA Technical Reports Server (NTRS)

    2005-01-01

    For 5 years, the cooperative agreement NCC3-763 has focused on the development and understanding of Sic-based composites. Most of the work was performed in the area of SiC fiber-reinforced composites for UEET and NGLT and in collaboration with Goodrich Corporation under a partially reimbursable Space Act Agreement. A smaller amount of work was performed on C fiber-reinforced SiC matrix composites for NGLT. Major accomplishments during this agreement included: Improvements to the interphase used in melt-infiltrated (MI) SiC/SiC composites which increases the life under stressed-oxidation at intermediate temperatures referred to as "outside-debonding". This concept is currently in the patent process and received a Space Act Award. Mechanistic-based models of intermediate temperature degradation for MI SiC/SiC Quantification and relatively robust relationships for matrix crack evolution under stress in SiC/SiC composites which serve as the basis for stress-strain and elevated temperature life models The furthering of acoustic emission as a useful tool in composite damage evolution and the extension of the technique to other composite systems Development of hybrid C-SiC fiber-reinforced SiC matrix composites Numerous presentations at conferences, industry partners, and government centers and publications in recognized proceedings and journals. Other recognition of the author's accomplishments by NASA with a TGIR award (2004), NASA's Medal for Public Service (2004), and The American Ceramic Society s Richard M. Fulrath Award (2005). The following will briefly describe the work of the past five years in the three areas of interest: SiC/SiC composite development, mechanistic understanding and modeling of SiC/SiC composites, and environmental durability of C/SiC composites. More detail can be found in the publications cited at the end of this report.

  5. Trihalomethane hydrolysis in drinking water at elevated temperatures.

    PubMed

    Zhang, Xiao-Lu; Yang, Hong-Wei; Wang, Xiao-Mao; Karanfil, Tanju; Xie, Yuefeng F

    2015-07-01

    Hydrolysis could contribute to the loss of trihalomethanes (THMs) in the drinking water at elevated temperatures. This study was aimed at investigating THM hydrolysis pertaining to the storage of hot boiled water in enclosed containers. The water pH value was in the range of 6.1-8.2 and the water temperature was varied from 65 to 95 °C. The effects of halide ions, natural organic matter, and drinking water matrix were investigated. Results showed that the hydrolysis rates declined in the order following CHBrCl2 > CHBr2Cl > CHBr3 > CHCl3. THM hydrolysis was primarily through the alkaline pathway, except for CHCl3 in water at relatively low pH value. The activation energies for the alkaline hydrolysis of CHCl3, CHBrCl2, CHBr2Cl and CHBr3 were 109, 113, 115 and 116 kJ/mol, respectively. No hydrolysis intermediates could accumulate in the water. The natural organic matter, and probably other constituents, in drinking water could substantially decrease THM hydrolysis rates by more than 50%. When a drinking water was at 90 °C or above, the first order rate constants for THM hydrolysis were in the magnitude of 10(-2)‒10(-1) 1/h. When the boiled real tap water was stored in an enclosed container, THMs continued increasing during the first few hours and then kept decreasing later on due to the competition between hydrolysis and further formation. The removal of THMs, especially brominated THMs, by hydrolysis would greatly reduce one's exposure to disinfection by-products by consuming the boiled water stored in enclosed containers. PMID:25898249

  6. Constitutive equations for meeting elevated-temperature-design needs

    SciTech Connect

    Pugh, C.E.; Robinson, D.N.

    1981-01-01

    Constitutive equations for representing the inelastic behavior of structural alloys at temperatures in the creep regime are discussed from the viewpoint of advances made over the past decade. An emphasis is placed on the progress that has been made in meeting the needs of the program whose design process is based in part on a design-by-inelastic-analysis approach. In particular, the constitutive equations that have been put into place for current use in design analyses are discussed along with some material behavior background information. Equations representing short-term plastic and long-term creep behaviors are considered. Trends towards establishing improved equations for use in the future are also described. Progress relating to fundamentals of continuum mechanics, physical modeling, phenomenological modeling, and implementation is addressed.

  7. Behavior of reinforcement SCC beams under elevated temperatures

    NASA Astrophysics Data System (ADS)

    Fathi, Hamoon; Farhang, Kianoosh

    2015-09-01

    This experimental study focuses on the behavior of heated reinforced concrete beams. Four types of concrete mixtures were used for the tested self-compacting concrete beams. A total of 72 reinforced concrete beams and 72 standard cylindrical specimens were tested. The compressive strength under uniaxial loading at 23 °C ranged from 30 to 45 MPa. The specimens were exposed to different temperatures. The test parameters of interest were the compressive strength and the temperature of the specimens. The effect of changes in the parameters was examined so as to control the behavior of the tested concrete and that of the reinforced concrete beam. The results indicated that flexibility and compressive strength of the reinforced concrete beams decreased at higher temperatures. Furthermore, heating beyond 400 °C produced greater variations in the structural behavior of the materials in both the cylindrical samples and the reinforced concrete beams.

  8. Evaluation of fatigue properties of 316FR stainless steel welded joints at elevated temperature

    SciTech Connect

    Kaguchi, Hitoshi; Koto, Hiroyuki; Fujioka, Terutaka; Taguchi, Kosei; Sukekawa, Masayuki

    1996-12-01

    316FR is an improved version of type 316 stainless steel for elevated temperature use with lower carbon content than conventional type 316 stainless steel. Fatigue properties of GTAW joints of 316FR stainless steel have been investigated. Heat affected zone (HAZ) of 316FR becomes harder than base metal. A method based on the stress-strain relationship of three elements, which are base metal, HAZ and weld portions, has been proposed and applied to the evaluations of fatigue tests. The tri-metal analysis model gives good agreements between experimental results and predicted fatigue lives of the 316FR welded joints. This material is to be used in the DFBR reactor in Japan.

  9. Elevated temperature cracking of RSP aluminum alloy 8009 - Characterization of the environmental influence

    NASA Technical Reports Server (NTRS)

    Porr, William C., Jr.; Leng, Yang; Gangloff, Richard P.; Reynolds, Anthony

    1991-01-01

    Degradation of the material properties of the Al alloy is examined to determine the effects of moist air and predissolved hydrogen on elevated-temperature fatigue and fracture resistance. Experiments are conducted at 175 C in both moist air and high vacuum with as-processed specimens and specimens that are vacuum-heat-treated. Fracture mechanics characterizations are made for initiation and propagation fracture toughnesses during rising load, fatigue-crack propagation kinetics, and sustained-load crack-growth rates. Time-dependent embrittlement at intermediate temperatures is identified in both plate and extrusion samples of the Al-Fe-Si-V alloy 8009. Intermediate temperature cracking is found to be the same for each case in both vacuum and moist air, and the vacuum heat treatment does not significantly affect the results.

  10. A Study on Fretting Fatigue Life in Elevated Temperature for Incoloy 800

    NASA Astrophysics Data System (ADS)

    Kwon, Jae Do; Woo, Seung Wan; Chung, Il Sup; Yoon, Dong Hwan; Park, Dae Kyu

    Incoloy 800, which is used within steam generator tubes, is a heat resistant material since it is an iron-nickel-chromium alloy. However, construction of a systematic database is needed to receive integrity data defecting insurance of specific data about room and elevated temperature fretting fatigue behavior for Incoloy 800. Accordingly, this study investigates the specific change in fatigue limitations under the condition of the fretting fatigue as compared to that under the condition of the plain fatigue by performing plain and fretting fatigue tests on Incoloy 800 at 320°C, real operating temperature and at room-temperature, respectively. The change in the frictional force is measured during the fretting fatigue testing against the repeated cycle, and the mechanism of fretting fatigue is investigated through the observation of the fatigue-fracture surface.

  11. An assessment of buffer strips for improving damage tolerance of composite laminates at elevated temperature

    NASA Technical Reports Server (NTRS)

    Bigelow, C. A.

    1981-01-01

    Buffer strips greatly improve the damage tolerance of graphite/epoxy laminates loaded in tension. Graphite/polyimide buffer strip panels were made and tested to determine their residual strength at ambient and elevated (177 C) temperature. Each panel was cut in the center to represent damage. Panels were radiographed and crack-opening displacements were recorded to indicate fracture, fracture arrest, and the extent of damage in the buffer strip after arrest. All panels had the same buffer strip spacing and width. The buffer strip material was 0 deg S-glass/PMR-15. The buffer strips were made by replacing narrow strips of the 0 deg graphite plies with strips of the 0 deg S-glass on either a one-for-one or a two-for-one basis. Half of the panels were heated to 177 + or - 3 C before and during the testing. Elevated temperature did not alter the fracture behavior of the buffer configuration.

  12. Elevated Temperature Properties of Titanium Carbide Base Ceramals Containing Nickel or Iron

    NASA Technical Reports Server (NTRS)

    Cooper, A L; Colteryahn, L E

    1951-01-01

    Elevated-temperature properties of titanium carbide base ceramals containing nickel or iron were determined in oxidation, modulus of rupture, tensile strength, and thermal-shock resistance. These materials followed the general growth law and exhibited two stages in oxidation. The following tensile strengths were found at 2000 degrees F: 13.3 weight percent nickel, 16, 150 pounds per square inch; 11.8 weight percent iron, 12,500 pounds per square inch; unalloyed titanium carbide, 16,450 pounds per square inch. Nickel or iron additions to titanium carbide improved the thermal-shock resistance, nickel more. The path of fracture in tensile and thermal-shock specimens was found to progress approximately 50 percent intergranularly and 50 percent transgranularly.

  13. Fatigue and flexural response of advanced carbon-carbon composites at room and elevated temperatures

    NASA Technical Reports Server (NTRS)

    Mahfuz, Hassan; Das, Partha S.; Jeelani, Shaik; Baker, Dean M.; Johnson, Sigurd A.

    1992-01-01

    The flexural response of SiC-coated carbon-carbon composites (ACC-4) at room and elevated temperatures is presented. Three-point bending tests were performed on virgin and mission-cycled specimens, and the variation in flexural strength is examined. The load-deflection behavior of the material at various temperatures is investigated, and the Weibull (1939) analysis of the strength data is performed. Micrographs of various cross sections in the damaged zone were taken, and the failure mechanisms are discussed. Fatigue tests were conducted under flexural loads, and the S-N diagram with the corresponding Weibull analysis are presented. Untested as well as fractured specimens under static and dynamic loading were C-scanned to identify the damaged zone and visualize the extent of the damage. Failure analyses are presented for both static and cyclic loading on the basis of NDE, the micrographs, and the experimental data.

  14. Generation of Constant Life Diagram under Elevated Temperature Ratcheting of 316LN Stainless Steel

    NASA Astrophysics Data System (ADS)

    Sarkar, Aritra; Nagesha, A.; Sandhya, R.; Mathew, M. D.

    2016-04-01

    Combined influence of mean stress and stress amplitude on the cyclic life under elevated temperature (823-923 K) ratcheting of 316LN austenitic stainless steel is discussed. Constant life Haigh diagrams have been generated, using different combinations of stress amplitude and mean stress. In the plastic domain, the allowable stress was found to increase or decrease with mean stress depending on the temperature and combination of mean stress - stress amplitude employed. Strong influence of dynamic strain aging (DSA) was found at 823 K which affected the mode of deformation of the material in comparison with 923 K. Failure mode expressed through a fracture mechanism map was found to change from fatigue to necking depending on the test temperature as well as combinations of mean stress and stress amplitude. Occurrence of DSA at 823 K proved to be beneficial by way of extending the safe zone of operation to higher R-ratios in comparison with 923 K.

  15. Microstructure and tensile properties of tungsten at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Shen, Tielong; Dai, Yong; Lee, Yongjoong

    2016-01-01

    In order to support the development of the 5 MW spallation target for the European Spallation Source, the effect of fabrication process on microstructure, ductile-to-brittle transition temperature (DBTT), tensile and fracture behaviour of powder-metallurgy pure tungsten materials has been investigated. A hot-rolled (HR) tungsten piece of 12 mm thickness and a hot-forged (HF) piece of about 80 mm thickness were used to simulate the thin and thick blocks in the target. The two tungsten pieces were characterized with metallography analysis, hardness measurement and tensile testing. The HR piece exhibits an anisotropic grain structure with an average size of about 330 × 140 × 40 μm in rolling, long transverse and short transverse (thickness) directions. The HF piece possesses a bimodal grain structure with about 310 × 170 × 70 μm grain size in deformed part and about 25 μm sized grains remained from sintering process. Hardness (HV0.2) of the HR piece is slightly greater than that of the HF one. The ductility of the HR tungsten specimens is greater than that of the HF tungsten. For the HF tungsten piece, specimens with small grains in gauge section manifest lower ductility but higher strength. The DBTT evaluated from the tensile results is 250-300 °C for the HR tungsten and about 350 °C for the HF tungsten.

  16. Investigation of the Compressive Strength and Creep Lifetime of 2024-T3 Aluminum-Alloy Plates at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Mathauser, Eldon E; Deveikis, William D

    1957-01-01

    The results of elevated-temperature compressive strength and creep tests of 2024-t3 (formerly 24s-t3) aluminum alloy plates supported in v-grooves are presented. The strength-test results indicate that a relation previously developed for predicting plate compressive strength for plates of all materials at room temperature is also satisfactory for determining elevated-temperature strength. Creep-lifetime results are presented for plates in the form of master creep-lifetime curves by using a time-temperature parameter that is convenient for summarizing tensile creep-rupture data. A comparison is made between tensile and compressive creep lifetime for the plates and a method that made use of isochronous stress-strain curves for predicting plate-creep failure stresses is investigated.

  17. Elevated Temperature Primary Load Design Method Using Pseudo Elastic-Perfectly Plastic Model

    SciTech Connect

    Carter, Peter; Sham, Sam; Jetter, Robert I

    2012-01-01

    A new primary load design method for elevated temperature service has been developed. Codification of the procedure in an ASME Boiler and Pressure Vessel Code, Section III Code Case is being pursued. The proposed primary load design method is intended to provide the same margins on creep rupture, yielding and creep deformation for a component or structure that are implicit in the allowable stress data. It provides a methodology that does not require stress classification and is also applicable to a full range of temperature above and below the creep regime. Use of elastic-perfectly plastic analysis based on allowable stress with corrections for constraint, steady state stress and creep ductility is described. This approach is intended to ensure that traditional primary stresses are the basis for design, taking into account ductility limits to stress re-distribution and multiaxial rupture criteria.

  18. Constitutive Equations for Use in Design Analyses of Long-life Elevated Temperature Components

    NASA Technical Reports Server (NTRS)

    Pugh, C. E.; Robinson, D. N.

    1983-01-01

    Design analysis needs and procedures relative to elevated temperature components in liquid metal fast breeder reactor (LMFBR) system were examined. The effects of the thermal transients on the pressure boundary components are enhanced by the excellent heat transfer properties of the liquid sodium coolant. Design criteria for high temperature nuclear reactor components recognize the potential occurrence of inelastic structural response. Specifically, criteria and limits were developed which reflect a recognition of this potential and employ design by analysis concepts that requires that inelastic (elastic-plastic and creep) analyses be performed. Constitutive equations to represent multiaxial time-dependent responses of LMFBR alloys are established. The development of equations applicable under cyclic loading conditions are outlined.

  19. An anisotropic thermomechanical damage model for concrete at transient elevated temperatures.

    PubMed

    Baker, Graham; de Borst, René

    2005-11-15

    The behaviour of concrete at elevated temperatures is important for an assessment of integrity (strength and durability) of structures exposed to a high-temperature environment, in applications such as fire exposure, smelting plants and nuclear installations. In modelling terms, a coupled thermomechanical analysis represents a generalization of the computational mechanics of fracture and damage. Here, we develop a fully coupled anisotropic thermomechanical damage model for concrete under high stress and transient temperature, with emphasis on the adherence of the model to the laws of thermodynamics. Specific analytical results are given, deduced from thermodynamics, of a novel interpretation on specific heat, evolution of entropy and the identification of the complete anisotropic, thermomechanical damage surface. The model is also shown to be stable in a computational sense, and to satisfy the laws of thermodynamics. PMID:16243703

  20. Evolution of Intermetallics, Dispersoids, and Elevated Temperature Properties at Various Fe Contents in Al-Mn-Mg 3004 Alloys

    NASA Astrophysics Data System (ADS)

    Liu, K.; Chen, X.-G.

    2015-12-01

    Nowadays, great interests are rising on aluminum alloys for the applications at elevated temperature, driven by the automotive and aerospace industries requiring high strength, light weight, and low-cost engineering materials. As one of the most promising candidates, Al-Mn-Mg 3004 alloys have been found to possess considerably high mechanical properties and creep resistance at elevated temperature resulted from the precipitation of a large number of thermally stable dispersoids during heat treatment. In present work, the effect of Fe contents on the evolution of microstructure as well as high-temperature properties of 3004 alloys has been investigated. Results show that the dominant intermetallic changes from α-Al(MnFe)Si at 0.1 wt pct Fe to Al6(MnFe) at both 0.3 and 0.6 wt pct Fe. In the Fe range of 0.1-0.6 wt pct studied, a significant improvement on mechanical properties at elevated temperature has been observed due to the precipitation of dispersoids, and the best combination of yield strength and creep resistance at 573 K (300 °C) is obtained in the 0.3 wt pct Fe alloy with the finest size and highest volume fraction of dispersoids. The superior properties obtained at 573 K (300 °C) make 3004 alloys more promising for high-temperature applications. The relationship between the Fe content and the dispersoid precipitation as well as the materials properties has been discussed.

  1. Smart materials and structures

    NASA Technical Reports Server (NTRS)

    Rogowski, Robert S.; Heyman, Joseph S.

    1993-01-01

    Embedded optical fibers allow not only the cure-monitoring and in-service lifetime measurements of composite materials, but the NDE of material damage and degradation with aging. The capabilities of such damage-detection systems have been extended to allow the quantitative determination of 2D strain in materials by several different methods, including the interferometric and the numerical. It remains to be seen, what effect the embedded fibers have on the strength of the 'smart' materials created through their incorporation.

  2. An Elevated-Temperature Tension-Compression Test and Its Application to Magnesium AZ31B

    NASA Astrophysics Data System (ADS)

    Piao, Kun

    Many metals, particularly ones with HCP crystal structures, undergo deformation by combinations of twinning and slip, the proportion of which depends on variables such as temperature and strain rate. Typical techniques to reveal such mechanisms rely on metallography, x-ray diffraction, or electron optics. Simpler, faster, less expensive mechanical tests were developed in the current work and applied to Mg AZ31B. An apparatus was designed, simulated, optimized, and constructed to enable the large-strain, continuous tension/compression testing of sheet materials at elevated temperature. Thermal and mechanical FE analyses were used to locate cartridge heaters, thus enabling the attainment of temperatures up to 350°C within 15 minutes of start-up, and ensuring temperature uniformity throughout the gage length within 8°C. The low-cost device also makes isothermal testing possible at strain rates higher than corresponding tests in air. Analysis was carried out to predict the attainable compressive strains using novel finite element (FE) modeling and a single parameter characteristic of the machine and fixtures. The limits of compressive strain vary primarily with the material thickness and the applied-side-force-to-material-strength ratio. Predictions for a range of sheet alloys with measured buckling strains from -0.04 to -0.17 agreed within a standard deviation of 0.025 (0.015 excluding one material that was not initially flat). In order to demonstrate the utility of the new method, several sheet materials were tested over a range of temperatures. Some of the data obtained is the first of its kind. Magnesium AZ31B sheets were tested at temperatures up to 250°C with strain rate of 0.001/s. The inflected stress-strain curve observed in compression at room temperature disappeared between 125°C and 150°C, corresponding to the suppression of twinning, and suggesting a simple method for identifying the deformation mechanism transition temperature. The temperature

  3. Elevated temperature tribology of cobalt and tantalum-based alloys

    SciTech Connect

    Scharf, T. W.; Prasad, S. V.; Kotula, P. G.; Michael, J. R.; Robino, C. V.

    2014-12-31

    This paper describes the friction and wear behavior of a Co–Cr alloy sliding on a Ta–W alloy. Measurements were performed in a pin-on-flat configuration with a hemispherically tipped Co-base alloy pin sliding on a Ta–W alloy flat from ambient to 430°C. Focused ion beam-scanning electron microscopy (FIB-SEM) and cross-sectional transmission electron microscopy (TEM) were used to identify the friction-induced changes to the chemistry and crystal structure in the subsurface regions of wear tracks. During sliding contact, transfer of material varied as a function of the test temperature, either from pin-to-flat, flat-to-pin, or both, resulting in either wear loss and/or volume gain. Friction coefficients (μ) and wear rates also varied as a function of test temperature. The lowest friction coefficient (μ=0.25) and wear rate (1×10–4 mm3/N•m) were observed at 430°C in argon atmosphere. This was attributed to the formation of a Co-base metal oxide layer (glaze), predominantly (Co, Cr)O with Rocksalt crystal structure, on the pin surface. Part of this oxide film transferred to the wear track on Ta–W, providing a self-mated oxide-on-oxide contact. Once the oxide glaze is formed, it is able to provide friction reduction for the entire temperature range of this study, ambient to 430°C. Furthermore, the results of this study indicate that glazing the surfaces of Haynes alloys with continuous layers of cobalt chrome oxide prior to wear could protect the cladded surfaces from damage.

  4. Elevated temperature tribology of cobalt and tantalum-based alloys

    DOE PAGESBeta

    Scharf, T. W.; Prasad, S. V.; Kotula, P. G.; Michael, J. R.; Robino, C. V.

    2014-12-31

    This paper describes the friction and wear behavior of a Co–Cr alloy sliding on a Ta–W alloy. Measurements were performed in a pin-on-flat configuration with a hemispherically tipped Co-base alloy pin sliding on a Ta–W alloy flat from ambient to 430°C. Focused ion beam-scanning electron microscopy (FIB-SEM) and cross-sectional transmission electron microscopy (TEM) were used to identify the friction-induced changes to the chemistry and crystal structure in the subsurface regions of wear tracks. During sliding contact, transfer of material varied as a function of the test temperature, either from pin-to-flat, flat-to-pin, or both, resulting in either wear loss and/or volumemore » gain. Friction coefficients (μ) and wear rates also varied as a function of test temperature. The lowest friction coefficient (μ=0.25) and wear rate (1×10–4 mm3/N•m) were observed at 430°C in argon atmosphere. This was attributed to the formation of a Co-base metal oxide layer (glaze), predominantly (Co, Cr)O with Rocksalt crystal structure, on the pin surface. Part of this oxide film transferred to the wear track on Ta–W, providing a self-mated oxide-on-oxide contact. Once the oxide glaze is formed, it is able to provide friction reduction for the entire temperature range of this study, ambient to 430°C. Furthermore, the results of this study indicate that glazing the surfaces of Haynes alloys with continuous layers of cobalt chrome oxide prior to wear could protect the cladded surfaces from damage.« less

  5. Exposure Of NIF Relevant Polymeric Samples To Deuterium-Tritium Gas At Elevated Temperature And Pressure

    SciTech Connect

    Ebey, P S; Dole, J M; Nobile, A; Schoonover, J R; Burmann, J; Cook, B; Letts, S; Sanchez, J; Nikroo, A

    2005-06-24

    The purpose of the experiments described in this paper was to expose samples of polymeric materials to a mixture of deuterium-tritium (DT) gas at elevated temperature and pressure to investigate the effects (i.e. damage) on the materials. The materials and exposure parameters were chosen with to be relevant to proposed uses of similar materials in inertial fusion ignition experiments at the National Ignition Facility. Two types of samples were exposed and tested. The first type consisted of 10 4-lead ribbon cables of fine manganin wire insulated with polyimide. Wires of this type are proposed for use in thermal shimming of hohlraums and the goal of this experiment was to measure the change in electrical resistance of the insulation due to tritium exposure. The second type of sample consisted of 20 planar polymer samples that may be used as ignition capsule materials. The exposure was at 34.5 GPa (5010 psia) and 70 C for 48 hours. The change in electrical resistance of the wire insulation will be presented. The results for capsule materials will be presented in a separate paper in this issue.

  6. Recovery Strategy and Mechanism of Aged Lithium Ion Batteries after Shallow Depth of Discharge at Elevated Temperature.

    PubMed

    Cui, Yingzhi; Du, Chunyu; Gao, Yunzhi; Yang, Jie; Zhang, Lingling; Guan, Ting; Yang, Lijie; Cheng, Xinqun; Zuo, Pengjian; Ma, Yulin; Yin, Geping

    2016-03-01

    Performance degradation of prismatic lithium ion batteries (LIBs) with LiCoO2 and mesocarbon microbead as active materials is investigated at an elevated temperature for shallow depth of discharge. Aged LIBs are disassembled to characterize the interface morphology, bulk structure, and reversible capacity of an individual electrode. It is found that the formation of interfacial blocking layer (IBL) on the anode results in the cathode state of charge (SOC) offset, which is the primary reason for the cathode degradation. The main capacity degradation of the anode is attributed to the IBL on the anode surface that impedes the intercalation and deintercalation of lithium ions. Because the full battery capacity is limited by the cathode during aging, the cathode SOC offset is the most important reason for the full battery capacity loss. Interestingly, the capacity of aged LIBs can be recovered to a relative high level after adding the electrolyte, rather than the solvent. This recovery is attributed to the relief of the cathode SOC offset and the dissolution of the anode IBL, which reopens the intercalation and deintercalation paths of lithium ions on the anode. Moreover, it is revealed that the relief of cathode SOC offset and the dissolution of anode IBL trigger and promote mutually to drive the recovery of LIBs. PMID:26848629

  7. Evaluation Of Liner Back-pressure Due To Concrete Pore Pressure At Elevated Temperatures

    SciTech Connect

    James, R.J.; Rashid, Y.R.; Liu, A.S.; Gou, B.

    2006-07-01

    GE's latest evolution of the boiling water reactor, the ESBWR, has innovative passive design features that reduce the number and complexity of active systems, which in turn provide economic advantages while also increasing safety. These passive systems used for emergency cooling also mean that the primary containment system will experience elevated temperatures with longer durations than conventional plants in the event of design basis accidents. During a Loss of Coolant Accident (LOCA), the drywell in the primary containment structure for the ESBWR will be exposed to saturated steam conditions for up to 72 hours following the accident. A containment spray system may be activated that sprays the drywell area with water to condense the steam as part of the recovery operations. The liner back-pressure will build up gradually over the 72 hours as the concrete temperatures increase, and a sudden cool down could cause excessive differential pressure on the liner to develop. For this analysis, it is assumed that the containment spray is activated at the end of the 72-hour period. A back-pressure, acting between the liner and the concrete wall of the containment, can occur as a result of elevated temperatures in the concrete causing steam and saturated vapor pressures to develop from the free water remaining in the pores of the concrete. Additional pore pressure also develops under the elevated temperatures from the non-condensable gases trapped in the concrete pores during the concrete curing process. Any buildup of this pore pressure next to the liner, in excess of the drywell internal pressure, will act to push the liner away from the concrete with a potential for tearing at the liner anchorages. This paper describes the methods and analyses used to quantify this liner back-pressure so that appropriate measures are included in the design of the liner and anchorage system. A pore pressure model is developed that calculates the pressure distribution across the concrete

  8. Gasket performance of SWG in ROTT and short term estimation at elevated temperature

    SciTech Connect

    Asahina, M.; Nishida, T.; Yamanaka, Y.

    1996-12-01

    This paper deals with the sealability at room temperature and the durability at elevated temperature of SWG (spiral wound gasket). The fillers in the gasket specimens are chosen as newly developed non-asbestos, asbestos and flexible graphite. The effects of inner and outer rings inserted in the gasket specimens on the new PVRC gaskets constants are examined by using the ROTT test procedure (room temperature tightness test). The durability of SWG at elevated temperature is estimated by using the weight loss of filler and the stress-deflection curve of SWG obtained after aging at elevated temperatures. As a result, the sealability and the durability of newly developed non-asbestos SWG is the same as asbestos SWG, and the durability of flexible graphite SWG at elevated temperatures in this method conform to the boundary temperature in field and it is shown that this method is available to estimate the durability of gaskets at elevated temperatures.

  9. Selection of flowing liquid lead target structural materials for accelerator driven transmutation applications

    SciTech Connect

    Park, J.J.; Buksa, J.J.

    1994-08-01

    The beam entry window and container for a liquid lead spallation target will be exposed to high fluxes of protons and neutrons that are both higher in magnitude and energy than have been experienced in proton accelerators and fission reactors, as well as in a corrosive environment. The structural material of the target should have a good compatibility with liquid lead, a sufficient mechanical strength at elevated temperatures, a good performance under an intense irradiation environment, and a low neutron absorption cross section; these factors have been used to rank the applicability of a wide range of materials for structural containment Nb-1Zr has been selected for use as the structural container for the LANL ABC/ATW molten lead target. Corrosion and mass transfer behavior for various candidate structural materials in liquid lead are reviewed, together with the beneficial effects of inhibitors and various coatings to protect substrate against liquid lead corrosion. Mechanical properties of some candidate materials at elevated temperatures and the property changes resulting from 800 MeV proton irradiation are also reviewed.

  10. Influence of Elevated Temperatures on Pet-Concrete Properties

    NASA Astrophysics Data System (ADS)

    Albano, C.; Camacho, N.; Hernández, M.; Matheus, A.; Gutiérrez, A.

    2008-08-01

    Lightweight aggregate is an important material in reducing the unit weight of concrete complying with special concrete structures of large high-rise buildings. Besides, the use of recycled PET bottles as lightweight aggregate in concrete is an effective contribution for environment preservation. So, the objective of the present work was to study experimentally the flexural strength of the PET -concrete blends and the thermal degradation of the PET in the concrete, when the blends with 10 and 20% in volume of PET were exposed to different temperatures (200, 400, 600 °C). The flexural strength of concrete-PET exposed to a heat source is strongly dependent on the temperature, water/cement ratio, as well as the content and particle size of PET. However, the activation energy is affected by the temperature, location of the PET particles on the slabs and the water/cement ratio. Higher water content originates thermal and hydrolytic degradation on the PET, while on the concrete, a higher vapor pressure which causes an increase in crack formation. The values of the activation energy are higher on the center of the slabs than on the surface, since concrete is a poor heat conductor.